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UNIVERSITY  OF  CALIFORNIA 


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28 


PSD  2338  9/77 


INFECTIOUS 
AND  PARASITIC  DISEASES 


LANGFELD 


"This  kingdom  (bacterial)  is  a  veritable  fairyland.  Its 
inhabitants  are  more  numerous  than  the  sands  of  the  sea, 
and  as  varying  in  their  functions  as  are  the  inhabitants  of 
the  animal  and  vegetable  kingdom."  "Only  a, "few  of 
them  work  serious  harm  to  man,  and  even  the  harm  which 
these  do  is  not  out  of  harmony  with  nature  as  a^whole. 
The  world  as  we  see  it  can  be  maintained  only  by^a  har- 
monious succession  of  life  and  death."  (Flick,  Consump- 
tion, a  Curable  and  Preventible  Disease.) 

"When  we  reahze  that  the  majority  of  all  deaths  is  still 
from  preventible  causes,  most  of  which  are  already  quite 
familiar  to  us,  it  is  manifest  that  this  must  be  in  a  large 
measure  due  to  an  indifference  on  our  part  to  put  into 
practice  even  the  knowledge  which  we  already  possess  for 
their  prevention."  (Abbott,  Hygiene  of  Transmissible 
Diseases.) 

"The  belief  is  growing  stronger  that  the  communicable 
diseases  are  more  often  spread  through  the  intermediation 
of  mild,  latent  and  unrecognized  cases  than  through  the 
agency  of  fomites,  that  is,  inanimate  objects."  (Rosenau, 
Disinfection  and  Disinfectants.) 


INTRODUCTION  TO 

INFECTIOUS  AND 
PARASITIC   DISEASES 

INCLUDING 

THEIR    CAUSE   AND 
MANNER    OF    TRANSMISSION 


BY 

MILLARD  LANGFELD,  A.B.,  M.B.,  (Johns  Hopkins) 

Professor  of   Bacteriology  and   Clinical  Medicine,  John  A.  Creighton  Med- 
ical College,  Omaha;  Visiting  Physician,  St.  Joseph's  and  Douglas 
County  Hospitals,  and  Bacteriologist,  the  Omaha  City 
Board  of  Health. 


With  an  Introduction  by  Lewellys  F.  Barker,  Professor  of 
Medicine  at  the  Johns  Hopkins  University 

WITH  THIRTY-THREE  ILLUSTRATIONS 


PHILADELPHIA 

P.  BLAKISTON'S  SON  &  CO. 

1012  WALNUT  STREET 
1907 


Copyright,  1907,  By  P.  Blakiston's  Son  &  Co. 


14^5" 


Printed  by 

The  Mapie  Press, 

York.  Pa. 


To  the 

memory  of  my  beloved  father 

"3)anlel  TCansfel^ 

this  book  in  grateful  remembrance 
is  dedicated 


PREFACE. 


Primarily  this  book  was  written  for  the  use  of  nurses, 
in  the  belief  that  by  broadening  their  comprehension  of 
infectious  and  parasitic  diseases  it  would  materially 
assist  them  in  performing  their  duties  more  intelli- 
gently, and  with  greater  satisfaction  to  themselves. 
Through  the  solicitations  of  several  medical  friends  who 
kindly  looked  over  my  manuscript,  and  who  were  of 
the  opinion  that  both  physicians  and  students  of  med- 
icine would  find  as  much  to  interest  them  in  its  pages 
as  would  nurses,  the  original  design  of  the  book  was 
altered  somewhat.  It  seemed  to  me  that  if  in  place 
of  the  conventional  (seriatum)  text-book  consideration 
of  the  above  diseases  the  fundamental  principles  which 
govern  all  were  substituted,  knowledge  of  wider  utility 
would  be  acquired,  and  with  less  effort,  because  much 
unimportant  detail  could  be  avoided.  It  was  my  aim, 
also,  by  reflecting  current  medical  thought  to  explain 
to  nurses  the  reasons  for  performing  many  duties  which 
they  are  merely  taught  to  do.  Then,  since  the  trained 
nurse's  position  as  medical  assistant  to  the  doctor  and 

vii 


viii  PREFACE. 

as  a  sanitarian  has  developed  into  one  of  such  extra- 
ordinary importance,  specific  information  in  regard 
to  these  offices  was  to  be  given  a  prominent  place. 
For  the  same  reasons,  chapters  on  "Bacteriology," 
"Parasites,"  and  "The  Collection  and  Examination  of 
Secretions  and  Excretions"  were  included  in  the  plan. 
Withal,  every  effort  was  to  be  made  to  be  lucid  in  style 
and  simple  in  treatment.  Of  nursing,  per  se,  I  was 
not  to  treat. 

The  present  volume  represents  my  efforts  to  embody 
the  above  ideas  in  a  book. 

My  obligation  to  various  authors  has  been  heavy, 
and  I  wish  I  could  make  suitable  acknowledgment  to 
every  one  upon  whom  I  have  drawn  for  material; 
but  the  character  of  the  book  obviously  makes  this 
impracticable.  Nevertheless,  to  Professor  Roger's 
"Introduction  to  the  Study  of  Medicine"  and  "Infec- 
tious Diseases,"  to  Dr.  Abott's  "Hygiene  of  Trans- 
missible Diseases,"  and  also  to  Dr.  Rosenau's  "Dis- 
infection and  Disinfectants,"  I  feel  reference  should 
be  made.  Furthermore,  I  would  be  lacking  in  grati- 
tude did  I  not  make  acknowledgment  to  my  alma 
mater,  the  Johns  Hopkins  Medical  School;  the  book 
really  owes  its  inception  to  the  scientific  spirit  and 
inspiring  personality  of  its  faculty. 

To  have  been  a  student  there  is  a  life-long  pleasurable 
memory,  and  a  distinction  which  I  feel  can  be  repaid 
only  in  small  measure  by  describing  my  efforts  as 


PREFACE.  ix 

feeble  amplifications  of  its  teachings.  Professor  Barker 
was  my  first  teacher  in  medicine,  and  to  him  I  am 
indebted  for  much  more  than  his  graciousness  in  review- 
ing these  pages  and  writing  the  introductory  note. 

The  only  originality  claimed  is  in  the  presentation 
of  the  subject  matter.  Save  in  a  few  instances,  specu- 
lation has  not  been  indulged  in,  and  only  accepted 
doctrines  have  been  adhered  to. 

Great  pleasure  was  taken  in  the  writing  of  these  pages, 
although  most  of  the  work  was  done  during  moments 
snatched  here  and  there  between  urgent  duties ;  whether 
I  was  justified  in  my  undertaking  can  only  be  told  if 
others  derive  either  pleasure  or  profit  in  their  perusal. 

Millard  Langfeld. 

203  McCague  Bldg.,  Omaha,  Neb. 
March  25,  1907. 


INTRODUCTORY  NOTE. 


This  volume  which  Dr.  Langfeld  has  written  is 
intended  as  an  introduction  to  the  subject  of  bacteriol- 
ogy, for  the  use  of  that  large  and  increasing  number  of 
people  who  are  interested  directly  or  indirectly  in  the 
subject,  but  who  have  been  unable  to  undergo  any 
practical  training  in  it.  I  have  had  the  opportunity  of 
reading  the  chapters  before  they  went  to  press,  and 
have  no  hesitation  in  recommending  the  book  to  the 
class  of  readers  for  which  it  is  intended.  The  presen- 
tation is  simple  and  clear,  and  the  author  has  carefully 
avoided  the  use  of  terms  and  the  discussion  of  questions 
which  would  be  unintelligible  to  beginners  in  the  sub- 
ject. It  is  his  hope  and  mine  that  many  may  be  led 
through  a  study  of  these  pages  to  undertake  sufficient 
practical  work  in  the  subject  of  bacteriology  to  permit 
them  to  apply  in  their  various  occupations  the  principles 
of  this  science  so  important  in  connection  with  medicine 
and  with  the  nursing  of  the  sick. 

Lewellys  F.  Barker. 

Baltimore,  Maryland. 
March  20,  1907. 


XI 


CONTENTS 


CHAPTER  I:    Causes  of  Disease i 

Health,  i — Disease,  i— Agents  of  disease,  mechanical, 
physical,  chemical,  animate,  3 — Infectious  agents,  5 — 
Parasite,  8 — Specific  and  non-specific  infectious  agents, 
9 — Specific  and  non-specific  infectious  diseases,  10 — 
Characteristics  of  infectious  diseases,  12 — Local  and  gen- 
eral infections,  19 — Combined  infections,  22 — Secondary 
infections,  23 — Self -limiting  nature  of  infectious  diseases, 
24— Antibodies,  25— Agglutinins,  27— -Opsonins,  27— 
Complications,  32 — Terminal  infections,  34 — Evolution 
of  disease,  34 — Communicable  diseases,  37. 

CHAPTER  H:    Bacteriology 38 

Arts  and  industries,  39— Saprophytes,  40— Pathogenic  and 
non-pathogenic  bacteria,  41 — Size,  42 — Multiplication,  42 
— Shape,  43 — Grouping,  44— Distribution,  45 — Specific 
and  non-specific  bacteria,  51 — Spores,  52 — Factors  neces- 
sary for  the  growth  of  bacteria,  53— Agents  harmful  to 
bacteria,  57 — Deodorant,  57 — Insecticides,  58. 

CHAPTER  III:    Phenomena  of  Infection 66 

Infectious  agents  in  disease,  68:  Number  of  bacteria  in, 
68— Portals  of  entry,  69— Virulence,  70 — Microbic  associa- 
tion (symbiosis),  71 — Conveyance  by  insects,  72.  The 
body  in  relation  to  infections,  73:  Predisposition,  74 — 
xiii 


99 


xiv  CONTENTS. 

Heredity,  76 — Race,  76 — Family,  79 — Individual,  80 — 
Environment,  81 — Region,  81 — Climate,  81 — Physical 
conditions,  85 — Season,  90 — Fasting,  poor  food,  etc.,  90 
— Occupation,  92 — Age,  94. 

CHAPTER  IV:    Inflammation 

Inflammation,  99 — Cardinal  symptoms  of  inflammation, 
loi — Leucocytes,  102 — Chemotaxis,  103 — Phagocytosis, 
104 — Leucocytosis,  105  —  Suppuration,  106 — Pyogenic 
bacteria,  107. 


CHAPTER  V:    Animal  Parasites 109 

Protozoa,  iii — Amoeba  DysentericB,  112 — Trypanosoma 
Gamhiense,  113 — Dum-Dum  fever,  113 — Plasmodium 
MalaricB,  113 — Nematodes,  116 — Guinea-worm,  116 — 
Filaria  Bancrojti,  118 — Filaria  Loa,  120 — Trichiuris 
trichiura,  121 — StrongyloidesintesHnalis,  122 — Trichinella 
Spiralis^  122 — Ascaris  lumbricoides,  124 — Oxyuris  ver- 
micularis,  125 — Uncinaria  duodenalis^  126.  Flat  worms, 
129:  Trematodes,  129: — Paragonimus  Westerm^nii,  130 
— Opisthorchis  Sinensis,  131 — Fasciola  hepatica,  132 — 
Schistosomumh(Ematohium,  132.  Cestodes,  133: — TcBnia 
saginata,  136 — Tcenia  Solium,  136 — Bothriocephalus  latus, 
137 — Dipylidium  Caninum,  138 — Hymenolepsis  nana, 
138.  Visceral  cestodes,  139: — Cysticercus  cellulosa,  139, 
— Tcpnia  echinococcus,  140.  Insects,  141 : — Parasitic  dip- 
tera,  141 — (Estrus  hominis,  142 — Derm^tobia  cyaniventris, 
143 — Compsomyiamacellaria,  143 — Sarcophaga  Carnaria, 
143 — Pulex  irritans  (flea),  144 — Sarcopsylla  penetrans 
(sand-flea),  144 — Bed-bug,  144 — Lice,  145 — Ascaris 
scabiei  (itch-mite),  148 — Leptus  Autumnalis  (harvest- 
mite),  149 — Ixodes  Ricinus  (wood-tick),  149. 


CONTENTS.  XV 

CHAPTER  VI:     Avenues  of  Exit  of  Infectious  Agents 

AND  Parasites  from  the  Body 151 

Expectoration  and  nasal  secretions,  155 — Feces,  156 — 
Urine,  160 — Skin,  161 — Blood  through  bites  of  insects, 
162 — Suppurations,  164. 

CHAPTER    VII:     Portals    of    Entry    of  Infectious 

Agents  and  Parasites  into  the  Body 166 

Through  wounds  of  skin  and  mucous  membranes,  173 — 
By  mouth  and  nose  through  air,  173 — By  mouth  through 
food  and  water,  175 — By  genito-urinary  tract,  181 — By 
placenta,  182 — Cryptogenic  (unknown  entrance),  183. 

CHAPTER  VIII:  Portals  of  Entry  and  Avenues  of 
Exit  of  Micro-organisms  in  the  Various  Diseases.  184 
Actinomycosis,  184— Anthrax,  185— Bubonic  plague,  186 
— Epidemic  cerebro-spinal  meningitis,  188 — Chicken-pox 
(varicella),  188— Cholera,  189 — Dengue,  190— Diphtheria, 
190— Dysentery  (amoebic),  192— Dysentery  (bacillary), 
192 — Erysipelas,  193 — Glanders,  194 — Gonorrhoea,  195 — 
Hydrophobia,  196 — Influenza,  197 — Leprosy,  197 — Ma- 
dura foot,  198— Malarial  fever,  198— Measles,  199 — 
Mumps,  200 — Pneumonia,  200 — Relapsing  fever,  201 — 
Rubella,  202 — Scarlet  fever,  202 — Small-pox,  207 — Epi- 
demic stomatitis,  205— Syphilis,  206— Tetanus,  207— 
Tuberculosis,  208 — T>3)hoid  fever,  209— Whooping- 
cough,  212 — Yellow  fever,  212. 

CHAPTER  IX:    Disinfectants  and  Disinfection 214 

Purpose  of,  214 — Heat,  216 — Gaseous  disinfectants,  218 
— Chemical  disinfectants,  liquids,  219 — Bichloride  of 
mercury,  221 — Formalin,  222 — Carbolic  acid,  222 — 
Tricresol,  223— Milk  of  lime,  224— Chloride  of  lime,  224. 


xvi  CONTENTS. 

CHAPTER  X:    Collection  and  Examination  of  Secre- 
tions AND  Excretions 226 

Sputum,  226 — Diphtheritic  cultures,  230 — Vomit,  232 — 
Test-meals,  234 — Blood  specimens,  236 — Typhoid  fever 
(Widal)  outfit,  236 — Malaria,  238 — Pus  and  other  dis- 
charges, 240 — Urine,  241 — Feces,  249. 

APPENDIX 253 

INDEX 255 


INFECTIOUS 
AND   PARASITIC  DISEASES. 

CHAPTER  I. 

CAUSES  OF  DISEASE. 

Since  disease  is  a  deviation  from  that  state  of  the 
body  which  is  called  health,  it  is  appropriate,  before 
taking  up  the  '^causes  of  disease,"  to  define,  briefly, 
what  health  and  disease  are. 

Health  may  be  defined  as  that  condition 
Health,     of  the  body  in  which  all  of  its  functions  are 

normally  performed,  to  the  end,  that  a 
feeling  of  mental  and  bodily  comfort  is  experienced.  It 
is  a  nice  balance,  or  equilibrium,  maintained  between 
our  bodies  and  the  surrounding  world.  Eating,  drink- 
ing, and  sleeping,  work,  play,  and  rest,  are  factors  that 
should  promote  a  general  feeling  of  well-being,  that 
in  turn  manifests  itself  in  the  desire  and  ability  to  eat, 
drink,  sleep,  work,  play,  and  rest,  all  normal  functions 
which  the  healthy  human  being  craves. 

Disease,  on  the  other  hand,  is  characterized 
Disease,     by  a  rupture  in  the  relationship  of  our 

bodies  to  our  surroundings,  which  leads 
to  disturbed  functions,  and  to  unusual  subjective  sen- 
sations and  objective  phenomena.     Whatever  breaks 


2  INFECTIOUS  AND^PAfeASITIC  DISEASES. 

the  harmony  of  health,  in  other  words,  whatever  causes 
disease,  always  acts  so  as  to  destroy  some  tissue,  or  to 
interfere  with  the  functions  of  some  organ.  The  mod- 
ern conception  of  the  causation  of  disease  no  longer 
gives  credence  to  the  belief  that  its  causes  are  novel 
and  mysterious,  but,  on  the  contrary,  from  indisputable 
evidence,  places  them  among  the  actual  phenomena  of 
the  physical  world.  Nor  does  it  admit  the  spontaneous 
development  of  disease  in  either  the  born  or  the  unborn, 
albeit  obvious  instances  to  the  contrary,  since  in  such 
cases  some  external  agency  has  previously  acted  directly 
or  indirectly  (e.g.,  through  a  parent)  as  a  first  cause, 
and  interrupted  the  orderly  continuity  of  the  normal 
functions.  Therefore,  no  matter  what  the  exciting 
cause  of  a  disease  may  be,  it  invariably,  and  primarily , 
comes  jrom  without  the  body. 

When  an  extraneous  cause  acts  injuriously  upon  a 
person,  his  organism  does  not  remain  passive,  but 
reacts  with  all  its  might  to  counteract  the  cause  and 
repair  any  defect  the  latter' s  presence  has  given  rise  to. 
This  power  of  the  body  to  protect  itself  lays  in  a  defen- 
sive mechanism  evolved  during  countless  ages  of  suc- 
cessful efforts  to  survive  destruction  against  harmful 
influences  in  the  universal  struggle  for  life.  So  nicely 
is  the  body's  mechanism  of  defense  adjusted,  that  con- 
stant re-adjustments  are  made  to  passing  dangers, 
under  ordinary  circumstances,  without  consciousness 
being  disturbed.     In  this  way  equilibrium  with  the 


CAUSES  OF  DISEASE.  j 

outside  world  is  maintained.  Should,  however,  a 
harmful  influence  be  unusually  strong,  then  the  reac- 
tions of  re-adjustment  to  which  it  gives  rise  are  corre- 
spondingly vigorous  and  wide-spread,  so  that  conscious- 
ness is  disturbed,  functions  are  corrupted,  and  most 
astonishing  changes  in  the  external  appearance  are 
observed.  These  phenomena  of  reaction  are  evidence 
of  the  battle  that  is  being  waged  by  the  body  against  a 
harmful  force,  and  collectively  they  constitute  the 
symptoms  oj  disease.  All  harmful  influences  are  pro- 
vocative of  disease ;  yet  disease  does  not  exist  unless  the 
reactions  or  symptoms  are  sufficiently  pronounced  as  to 
upset  the  orderly  unconscious  functioning  of  the  body. 

Diseased  states  are  also  called  morbid  or  pathological; 
wherefore  morbific  or  pathological  causes  are  those 
that  bring  about  disease.  The  causes  of  disease  are 
often  spoken  of  as  agents.  We  divide  the  agents  of 
disease  into  four  classes,  mechanical,  physical,  chemical, 
and  animate. 

A  blow  which  breaks  a  bone,  an  obstruction 
Mechanical,  to  respiration  due  to  a  foreign  body  lodging 

in  the  larynx,  a  rupture  of  the  abdominal 
wall  that  permits  a  loop  of  the  intestines  to  protrude, 
are  all  instances  of  diseases  due  to  mechanical  agents. 

Similarly,  alterations  in  the  surrounding 
Physical.        medium,    as    for   example,    ascending    to 

great  heights,  or  working  at  great  depths 
under  pressure,  produce  respectively  mountain-climbers' 


4  INFECTIOUS  AND  PARASITIC  DISEASES. 

disease  and  divers'  paralysis — two  well-recognized 
affections,  the  result  of  physical  agents. 

That  diseases  are  often  brought  about 
Chemical  through  chemical  agents  scarcely  needs 
Agents,      illustration  on  account  of  the  frequency 

of  such  cases  being  reported  by  the  Press, 
and  the  familiarity  of  the  average  person  with  the 
dangerous  character  of  many  chemicals,  notably  the 
poisons.  Ptpmain  poisoning,  which  comes  from  eating 
various  foods  that  have  undergone  a  peculiar  decom- 
position; arsenical  poisoning,  numerous  cases  of  which 
were  reported  in  London,  England,  a  few  years  ago, 
in  which  the  arsenic  was  traced  to  the  glucose  in  beer; 
and  painters'  colic,  or  lead  colic,  a  disease  common  in 
those  whose  occupations  bring  them  into  close  contact 
with  lead,  are  examples  of  diseases  of  chemic  origin. 
Indeed,  among  the  causes  of  disease,  the  chemical 
agents  are  by  far  the  most  numerous  and  the  most 
important,  in  as  much  as  the  majority  of  diseased 
states  are  fundamentally,  or  coincidentally,  of  a  chem- 
ical nature.  Most  of  the  physical  and  mechanical 
agencies,  through  the  injuries  they  inflict  on  tissues, 
are  thereby  transformed  into  chemical  irritants,  since 
the  resulting  reactions  follow  largely  as  a  result  of  the 
absorption  of  dead  and  useless  material.  For  example : 
A  person  is  severely  burned,  yet  survives  three  days. 
He  does  not  die  as  a  direct  result  of  the  physical  agent, 
fire,  but  from  poisoning  in  one  of  the  two  ways;  namely. 


CAUSES  OF  DISEASE.  5 

either  so  large  a  surface  of  the  cuticle  was  destroyed 
that  the  respiratory  and  excretory  functions  of  the  skin 
were  interrupted,  so  that  poisoning  followed  the  reten- 
tion of  products  which  should  have  been  excreted  from 
the  body;  or,  poisoning  resulted  from  absorption  of  the 
detrimental  products  into  which  the  skin  was  converted 
by  the  fire. 

Similarly,  in  diseases  the  result  of  mechanical  forces, 
while  the  earliest  phenomena  are  the  direct  result  of 
the  injury  (shock,  for  example),  the  later  reactions 
follow  as  a  sequel  to  the  absorption  of  dead  tissues 
and  inflammatory  products.  Indeed,  reconstruction  of 
tissues,  e.g.,  bone,  etc.,  is  initiated  by  these  very  prod- 
ucts being  absorbed,  and,  thereby  reflexly  irritating 
into  action  those  tissues  and  functions  that  bring  about 
repair. 

The  fourth  group  into  which  we  divide 

Animate     the    agents    of    disease    is    the    animate. 

Agents.       Animate    agents    comprise    two    classes, 

parasites  and  infectious  agents,   both  of 

which   may   be   found   among   either   the   animal   or 

vegetable  kingdom. 

Before  the  dawn  of  bacteriology,  phys- 
Infectious  icians  had  already  applied  the  term,  infec- 
Agents.  tious,   to  diseases  that,   symptomatically, 

conformed  to  a  certain  type  and  were  con- 
veyed through  the  air.     Early  in  their  career,  bacteriol- 


6  INFECTIOUS  AND  PARASITIC  DISEASES. 

ogists  discovered  that  a  number  of  the  infectious 
diseases  were  due  to  bacteria  and,  rather  hastily,  it 
must  be  confessed,  concluded  that  all  of  this  class  had 
a  similar  origin.  So  they  described  an  infectious 
disease  as  ''a  morbid  or  diseased  state  of  the  body  due 
to  the  invasion  and  growth  of  bacteria."  Somewhat 
later  it  was  seen  that  they  had  gone  too  far  in  formulat- 
ing this  definition  for  infectious  diseases,  because  a 
certain  number  were  discovered  which  owe  their  origin 
to  animate  agents  that  are  not  bacteria,  namely,  to 
moulds  and  protozoa.* 

Hence  it  has  followed  that  the  designation  ''infectious 
disease"  is  restricted  in  its  application  to  diseases  which 
conform  to  a  certain  type,  and  ''infectious  agent"  to 
a  living  organism, |  microscopic  in  size,  that  is  capable 
of  producing  an  infectious  disease.  So  far  as  we  know, 
only  three  types  of  organisms  produce  infectious  diseases, 
namely,  bacteria,  moulds  and  protozoa,  certain  species 
of  each  comprising  the  infectious  agents.  At  present 
bacteria  constitute  the  vast  majority,  but  it  is   fast 

*  Protozoa  (literally,  first  animal)  are  the  simplest  organisms  which 
clearly  belong  to  the  animal  kingdom.  The  characteristic  which  dis- 
tinguishes them  from  all  other  groups  of  animals  is  the  fact  that  each 
protozoan  consists  of  a  single  cell. 

t  Organism — composed  of  organs  functionally  necessary  for  the  ex- 
istence of  the  individual  or  race.  Although  unicellular  plants  and 
animals  have  no  organs,  yet,  since  they  perform  functions  analogous  to 
those  of  the  higher  forms  of  living  matter,  we  are  correct  in  considering 
them  organisms. 


CAUSES  OF  DISEASE.  7 

becoming  evident  that  both  protozoa  and  moulds  are 
of  almost,  if  not  of  equal  importance,  as  causative 
factors  in  infectious  diseases;  and  that  besides  these, 
there  are  other  microscopic  and  ultra-microscopic 
forms  of  life,  not  included  in  the  three  groups,  that  are 
playing  a  similar  role.  For  these  reasons  we  conclude 
that  the  only  defensible  definition  of  an  infectious  agent 
is  that  it  is  either  an  animal  or  vegetable  organism, 
microscopic  in  size,  which  produces  an  infectious 
disease.  It  will  be  observed,  from  the  point  of  view 
of  this  definition,  that  we  classify  the  organisms  that 
produce  infectious  diseases  not  by  their  place  in  the 
animal  or  vegetable  kingdom,  but  by  the  effects  they 
produce  in  the  living  body. 

The  animate  agents,  it  will  be  remembered,  we 
divided  into  two  classes,  parasites,  and  infectious  agents. 
The  designations  have  reference  both  to  the  manner 
in  which  the  agents  live  upon  the  body,  and  the  phenom- 
ena their  presence  give  rise  to;  their  place  in  either 
animal  or  vegetable  kingdom  is  again  disregarded. 
The  mode  of  action  of  the  infectious  agent  is  character- 
istic, and  markedly  different  from  that  of  the  parasite. 
When  it  enters  a  living  body,  it  aims  directly  at  the 
destruction  of  the  latter.  It  multiplies  rapidly,  tends 
to  scatter  its  broods  throughout  the  tissues,  and  all 
the  while  gives  off  the  most  powerful  poisons  known. 
This  agent  is  wickedly  implacable,  neither  giving  nor 
asking  quarter.     ThQ  battle  that  it  wages  with  the  body 


8  INFECTIOUS  AND  PARASITIC  DISEASES. 

can  terminate  only  by  the  destruction  of  one  of  the 
combatants. 

In  contrast  to  this  monster  evil  is  the  lesser, 
Parasite,    the  parasite.     A  parasite  is  an  organism 

that  lives  within  or  upon  another  organism 
called  the  host.  The  parasite's  purpose  is  an  easy 
living  at  the  expense  of  the  host.  It  subtly  recognizes 
that  it  is  to  its  interest  not  to  inflict  too  great  an  injury. 
If  perchance  it  causes  the  death  of  the  host,  it  is  an 
accident.  It  seldom  invades  the  body  generally. 
From  the  foregoing  is  seen  the  reason  for  drawing  a 
distinction  between  parasites  and  infectious  agents 
based  upon  their  mode  of  action  and  the  effects  they 
produce.  It  should  be  remembered,  however,  that 
parasites  and  infectious  agents  are  not  necessarily 
represented  by  distinct  organisms.  Indeed,  the  same 
microbe  may  live  upon  our  bodies,  or  within  its  cavities, 
at  one  time  as  a  parasite,  and  at  another  time  be  the 
cause  of  an  infectious  disease.  The  germ  of  pneu- 
monia is  a  constant  inhabitant  of  almost  everyone's 
mouth,  leading  there  a  harmless  parasitic  existence, 
yet  let  the  vital  powers  be  reduced  through  fatigue, 
exposure,  or  cold,  and  it  becomes  an  infectious  agent 
through  the  disease  (pneumonia)  which  it  provokes. 
The  difference  between  a  germ  that  is  at  one  time  a 
parasite,  and  at  another  time  an  infectious  agent, 
depends  in  the  latter  case  upon  the  power  it  has  of 
producing  its  specific  poison,  and  also  upon  its  chance 


CAUSES  OF  DISEASE.  9 

of  finding  lodgment  in  an  appropriate  situation  within 
the  body.* 

Infectious  agents  are  divided  into  those 
Specific  and  that  are  specijic,  and  those  that  are  non- 
NoN-sPECiFic  specific.  By  specific  is  understood  an 
Infectious  organism  that  ahvays  provokes  the  same 
Agents.  disease;  at  the  same  time  it  impHes  that 

it  is  the  only  exciting  cause  of  that  disease. 
The  microbes  which  cause  typhoid  fever,  diphtheria, 
plague,  etc.,  are  specific  agents,  because  they  are  the 
only  germs,  respectively,  that  can  give  rise  to  these 
diseases. 

A  non-specific  agent  is  an  organism  whose  entrance 
into  the  body  is  not  necessarily  followed  by  the  same 
disease,  in  fact,  its  effects  are  particularly  characterized 
by  their  dissimilarity;  besides,  its  action  is  duplicated 
by  other  non-specific  agents.  The  streptococcus 
pyogenes  is  a  most  excellent  example  of  a  non-specific 
agent.  The  following  are  some  of  the  diseases  it 
provokes:  Erysipelas,  puerperal  fever  (child-bed  fever), 
tonsillitis,  peritonitis,  abscess,  etc.,  all  affections  that 
exhibit  a  widely  divergent  symptomatology,  and  each  one 
of  which  may  result  from  entrance  into  the  body  of 
an  entirely  different  species  of  bacterium. 

*From  one  view-point,  all  infectious  agents  are  parasites,  just  as  we 
will  see  later  they  may  also  be  saprophytes.  But  the  true  parasite  is 
never  an  infectious  agent. 


lo         INFECTIOUS  AND  PARASITIC  DISEASES. 

Infectious  diseases  are  divided  into  the 
Specific  and  specific  and  the  non-specific  according 
Non-specific  as  they  result  from  a  specific  or  non- 
Infectious  specific  agent.  There  are  some  infectious 
Diseases.       diseases,  however,  in  which  the  etiological 

factor  is  not  known,  yet  they  are  classed 
with  the  specific  maladies.  This  is  done  because  the 
symptomatology  of  each  is  characteristic,  and  because 
any  one  of  them  in  one  individual  never  gives  rise  in 
another,  who  may  contract  it,  to  a  different  disease. 
In  this  class  of  specific  diseases,  of  which  the  causes 
are  not  known,  is  small-pox,  scarlet  fever,  measles, 
chicken-pox,  etc.  These  same  diseases  are  also  classed 
as  infectious,  but  entirely,  it  should  be  noted,  on  account 
of  their  close  resemblance  to  those  infectious  diseases 
whose  determining  factor  is  positively  known  to  be  a 
micro-organism. 

In  the  list  of  infectious  diseases  of  known  and  unknown 
etiology  which  follows,  it  will  perhaps  come  as  a  sur- 
prise to  the  student  that  the  cause  of  so  many  diseases 
is  as  yet  unknown ;  and  that  those  of  unknown  etiology' 
include  many  of  our  most  common  diseases.  He 
might  well  ask  the  question,  why  have  the  causes  of 
these  every-day  diseases  not  been  discovered?  There 
are  probably  two  chief  reasons :  First,  because  the  causes 
have  been  sought  for  as  if  they  must  be  bacteria, 
whereas  they  very  likely  belong  to  entirely  different 
genuses  of  organisms;  and  second,  because  the  causes 


CAUSES  OF  DISEASE. 


II 


of  some  diseases,  at  least,  are  probably  ultra-micro- 
scopic, i.e.,  too  minute  to  be  made  out  with  the  magnify- 
ing powers  of  the  present  microscope. 

It  will  also  be  noticed  that  syphilis  is  placed  under 
both  groups.  This  is  done  because,  from  the  evidence 
accumulated  thus  far,  it  seems  quite  probable  that  the 
treponema  pallidum  (spirochceta  pallida)  of  Schaudinn 
and  Hoffman  is  the  etiological  factor. 


SPECIFIC    INFECTIOUS 

DISEASES  OF  KNOWN 

ORIGIN. 

GONORRHCEA. 

Epidemic     Cerebro  -  spinal 

Meningitis. 
Pneumonia  (Lobar). 
Tuberculosis. 
Leprosy. 

Glanders  (Farcy). 
Tetanus  (Lock-jaw). 
Diphtheria. 
Asiatic  Cholera. 
Anthrax. 
Typhoid  Fever. 

Bubonic  Plague. 

Influenza  (La  Grippe). 

Malta  Fever. 

Relapsing  Fever. 

Acute    Specific    Dysentery 
(Bacillary  Dysentery). 

Actinomycosis. 

Mycetoma  (Madura  Foot). 

Malarial  Fever. 

Amcebic  Dysentery. 

Syphilis. 


SPECIFIC    INFECTIOUS 

DISEASES  OF  UNKNOWN 

ORIGIN. 

Epidemic  Parotitis  (Mumps). 

Syphilis. 

Rabies  (Hydrophobia). 

Yellow  Fever. 

Measles. 

Whooping-cough. 

Scarlatina  (Scarlet  Fever). 

Variola  (Small-pox). 

Typhus  Fever. 

Vaccinia  (Cow-pox,  Vaccina- 
tion). 

Varicella  (Chicken-pox). 

Rubella  (Rotheln). 

Dengue  (Break-bone  Fever). 

Rheumatic  Fever  (Rheumat- 
ism). 

Beri-beri. 

Glandular  Fever  (?). 

Aphthous  Fever  (Foot  and 
Mouth  Disease). 

Chancroid. 

Trachoma  (Egyptian  Ophthal- 
mia). 


12         INFECTIOUS  AND  PARASITIC  DISEASES. 

Character-  An  infectious  disease  follows  a  cycle,  or 
isTics  OF  course,  which  is  typical  of  the  class  '^infec- 
Infectious  tious  diseases."  To  be  sure,  there  are 
Diseases.  variations  from  the  type,  sometimes  very 
pronounced,  yet  certainly  never  greater  than  one  would 
anticipate  in  view  of  the  differences  exhibited  by  people 
in  general.  Moreover,  the  infectious  agents  causing 
them  are  subject  to  great  variations  in  disease-producing 
power,  a  fact  which  influences  the  character  of  the 
infection  either  for  better  or  for  worse.  Concerning 
these  differences  in  pathogenicity  as  exhibited  by  infec- 
tious agents,  we  shall  have  much  to  say  in  a  succeeding 
chapter.  In  this  course  or  cycle  of  an  infectious 
disease,  four  stages  are  commonly  admitted: 

1.  An  incubation  period. 

2.  A  period  of  invasion. 

3.  A  stationary  period. 

4.  A  period  of  decline. 

These  periods,  or  stages,  of  an  infectious  disease 
were  first  created  upon  purely  clinical  grounds;  but 
they  have  been  retained,  because  they  are  in  entire 
harmony  with  modern  discovery  and  experiment,  a 
fact  which  adds  another  laurel  to  the  fame  of  those  dear 
old  practitioners  who  knew  absolutely  nothing  of  the 
science  of  bacteriology.  Besides,  these  periods  as 
named  by  them,  remarkable  to  say,  graphically  describe 
the  progress  of  microbic  action  from  the  beginning  of 
a  disease  to   its  termination.     An   infectious  disease 


CAUSES  OF  DISEASE.  13 

must  be  regarded  as  a  battle  to  the  death  between  the 
body,  on  the  one  hand,  and  an  infectious  agent  on  the 
other;  and  as  the  symptoms  of  each  period  correspond 
to  various  phases  in  the  battle,  we  are  able  to  recognize 
which  side,  for  the  nonce,  has  the  upper  hand. 

The  incubation  period  is  the  time  that 
Incubation  elapses  between  the  entrance  of  the  disease- 
Period.  causing  microbe  into  the  body  and  the 

onset  of  the  symptoms. 
When  a  person  takes  a  drug  which  has  the  property 
of  inducing  sleep,  e.g.,  opium,  or  a  stimulant,  such  as 
whisky,  there  is  observed  an  appreciable  period  between 
the  ingestion  of  either,  and  the  beginning  of  the  phenom- 
ena which  are  characteristic  for  each  drug.  If  we 
follow  these  phenomena,  it  is  observed  that  according 
to  the  quantity  taken,  after  they  first  began  to  appear, 
there  is  a  gradual  increase  in  the  number  and  intensity 
of  the  symptoms  to  a  certain  point,  when  they  are 
maintained  for  a  variable  period.  Finally,  there  is  a 
gradual  lessening  of  the  influence  until  the  drug  is 
eliminated  from  the  body.  After  the  elimination  there 
remain  such  phenomena  as  are  the  result  of  the  removal 
of  the  influence,  and  the  re-adjustment  of  the  economy 
to  its  normal  state.  The  phenomena  just  described 
only  follow  in  case  a  dose  of  sufficient  size  has  been 
ingested,  the  amount  varying,  naturally,  with  the 
individual.  However,  when  that  quantity  which  will 
produce  symptoms  has  been  reached,  the  results  are 


14         INFECTIOUS  AND  PARASITIC  DISEASES. 

directly  dependent  upon  the  amount  taken.  There 
is  no  increase  of  the  drug  within  the  body. 

When,  however,  we  come  to  study  the  action  of  an 
infectious  agent  upon  the  body,  we  find  the  same 
interval  of  time  between  the  entrance  of  the  infectious 
agent  and  the  onset  of  the  symptoms,  but  there  is  a 
very  great  difference  in  the  events  that  take  place  to 
produce  the  reactions.  The  amount  of  opium  or 
whisky  ingested  is  fixed,  so  that  whatever  the  effect,  it 
results  from  just  that  amount.  When  infectious  agents 
enter  the  body,  however,  they  at  once  begin  to  multiply 
in  enormous  numbers,  giving  off  all  the  while  as  a 
product  of  their  activity  most  powerful  poisons  (toxins) . 
When  a  sufficient  amount  of  poison  has  been  generated, 
symptoms  of  the  disease  appear.  In  other  words,  the 
infectious  agents  that  gain  an  entrance  into  the  body 
have  not  of  themselves  sufficient  power  to  produce  the 
disease,  but  act  through  their  facility  of  increasing  their 
numbers.  It  is  self-evident,  therefore,  why  this  period 
is  called  the  "incubation  period,"  since  it  "corresponds 
to  the  development  (multiplication)  of  the  pathogenic 
agents."  Clinically  the  incubation  period  is  also 
known  as  the  latent  period. 

The  incubation  period  varies  as  to  time  in  different 
diseases,  and  in  different  cases  of  the  sam.e  disease. 
It  may  only  be  a  few  hours,  as  in  erysipelas,  or  it  may 
extend  over  months  and  years,  as  in  hydrophobia  and 
leprosy.     This  period  is  of  very  great  importance  from 


CAUSES  OF  DISEASE. 


IS 


a  hygienic  standpoint,  in  that  it  affects  the  length  of 
quarantine  imposed  upon  individuals  exposed  to  con- 
tagious diseases.  The  following  table  taken  principally 
from  Roger's  ''Infectious  Diseases"  is  worthy  of  careful 
study. 

INCUBATION    PERIOD    OF  VARIOUS   INFECTIOUS 
DISEASES. 


Average. 

Minimum. 

Maximum. 

Anthrax 

2 

days 

I  day 

3  days 

Bubonic  Plague 

4-6 

2     *' 

7      " 

Chancroid 

1-2 

I     " 

3      " 

Cholera 

2-4 

I     " 

6      " 

Diphtheria 

2 

2     " 

15      " 

Erysipelas 

4-6 

3  hours 

22      ** 

Influenza 

3-4 

I  day 

5      " 

Glanders 

3-5 

24  hours 

3  months 

Gonorrhoea 

3-5 

I  (?)-2  days 

I -several  weeks 

Mumps 

15 

7  days 

30  days 

Malarial  Fever 

6-10 

99  hours 

several  months 

Recurrent  Fever 

5-6 

86      " 

8  days 

Measles 

9 

4  days 

14      '' 

Hydrophobia 

20-60 

13  " 

18  mos.  to  3  yrs 

Rubeola 

18 

s    " 

21  days 

Scarlatina 

2-5 

7  hours 

7  weeks 

Small-pox 

12 

7  days 

15  days 

Syphilis 

20-30 

10      " 

50      " 

Tetanus  (Lock-jaw) 

2-3 

2  hours 

35      " 

Typhoid  Fever 

14 

2  days  (?) 

21      " 

Typhus  Fever 

12 

0  (?) 

23      " 

Vaccinia 

3 

2  days 

7     " 

i6         INFECTIOUS  AND  PARASITIC  DISEASES. 


Average. 

Minimum. 

Maximum. 

Varicella 

14-15  days 

13  days 

19  days 

Whooping-cough 

8 

2      '' 

8      '' 

Yellow  Fever 

3-4      " 

2      '' 

6      " 

Leprosy 

(?)^ 

(?) 

32  years 

Tuberculosis 

(  ?)  incubation  period  frequently  long. 

Dengue 

4       days 

3  days 

5  days 

Pneumonia 

24  hours 

(?) 

2  or  more  days 

Dysentery  (Bacillary)  8       days 

6  days 

48  hours 

Malta  Fever 

6-10    " 

(?) 

10  days 

Beri-beri 

Several  months  (?) 

During  the  incubation  period  symptoms 
Period  of  are  wanting,  and,  as  far  as  the  person  is 
Invasion.        aware,  he  experiences  nothing  to  indicate 

that  he  is  not  in  normal  health.  When, 
however,  the  body  awakens  to  the  impending  danger,  it 
brings  its  defensive  forces  into  play  in  an  effort  to  throw 
off  the  infectious  agents  and  their  toxins.  Chnically, 
these  reactions  are  represented  by  the  first  symptoms 
of  disease,  and  are  known  as  the  ''symptoms  of  onset." 
They  indicate  that  invasion  of  the  body  by  an  infectious 
agent  has  taken  place.  It  is  for  this  reason  that  this 
period  is  spoken  of  as  the  period  of  invasion. 

The  period  of  invasion  also  differs  in  various  diseases, 
and  in  various  cases  of  the  same  disease.  The  symp- 
toms of  invasion  may  appear  with  startling  suddenness, 
as  the  chill  which  occurs  at  the  onset  of  pneumonia,  or 
the  convulsion  in  children  which  initiates  most  of  the 
eruptive  fevers;  or  they  may  develop  so  gradually  as 


CAUSES  OF  DISEASE.  17 

to  make  it  impossible  for  the  patient  to  say  when  he 
really  began  to  feel  ill.  This  slow  insidious  manner 
of  onset  is  the  rule  in  typhoid  fever  and  pulmonary 
tuberculosis. 

After  the  period  of  invasion  comes  the 
Stationary  stationary  period,  the  symptoms  of  which 
Period.  are  so  characteristic  for  each  particular 

infectious  disease  as  to  form  the  basis  for 
our  classification  of  infectious  diseases  in  general,  and 
of  identification  of  any  one  in  particular.  If  the 
invasion  be  sudden,  the  stationary  period  is  usually 
quickly  reached  (in  pneumonia,  a  few  hours) ;  if  gradual, 
the  stationary  period  may  be  prolonged  a  week  or  more 
(e.g.,  typhoid  fever).  The  stationary  period  presents 
more  or  less  uniformity  in  symptoms,  with  ameliora- 
tions or  aggravations  of  the  symptoms  correspond- 
ing to  oscillations  of  advantage  of  either  body  or 
germ. 

Variations  from  the  type  of  the  stationary  period  in 
any  infectious  disease  also  occur  with  a  fair  degree  of 
frequency.  The  stationary  period  may  be  cut  short 
by  the  body-forces  being  marshaled  at  the  onset,  and 
the  disease  end  there ;  or  it  may  be  prolonged  far  beyond 
the  average  limits  for  the  disease.  On  the  other  hand, 
the  microbes  may  get  the  upper  hand  from  the  start, 
stifle  (in  their  incipiency)  the  body's  efforts  to  react 
and  close  the  picture  even  before  the  stationary  period 
had   really  begun.    However,   these   courses   are   not 


i8         INFECTIOUS  AND  PARASITIC  DISEASES. 

typical;  in  the  typical  case,  unless  the  battle  is  decided 
in  favor  of  the  microbes,  the  stationary  period  passes 
into  the  period  oj  decline.  Where  the  stationary  period 
of  any  disease  is  abbreviated  by  recovery,  we  speak  of 
the  disease  as  having  been  aborted ;  where  abbreviation 
or  prolongation  of  any  disease  occurs,  or  where  marked 
variations  from  the  type  take  place,  the  disease  is 
spoken  of  as  having  pursued  an  aberrant  form. 

The  period  of  decline  is  expressive  of  the 

Period  of    victory  that  the  body  has  won  over  the 

Decline.       infecting  agents.     This  period  is  taken  up 

with  the  physiological  re-adjustments  and 

anatomical  repairs  necessary  to  bring  the  body  back 

to  health. 

Precisely  as  the  onset  of  a  disease  may  be 

Crisis  and    either   sudden   or   gradual,    so   may   the 

Lysis.  decline  be  characterized  either  by  a  most 

astonishingly   rapid    amelioration    of    the 

symptoms,  or  by  slow,  progressive  improvement.     In 

the  former  case  we  speak  of  termination  of  the  disease 

by  crisis,  in  the  latter,  by  lysis. 

Termination  by  crisis  is  well  illustrated  by  pneumonia, 
termination  by  lysis,  by  typhoid  fever.  Crisis  is 
perhaps  the  most  peculiar  and  mystifying  phenomenon 
that  ever  occurs  in  disease.  Always  awaited  with  so 
much  anxiety,  when  it  has  happened  it  may  well  be 
joyously  received,  since  it  conveys  to  the  physician  the 
knowledge  that  recovery,  "oj  which  it  is  the  result,^ 


CAUSES  OF  DISEASE  19 

not  the  cause,  has  been  effected.  And  the  same  is 
true  of  lysis,  it  is  the  harbinger  of  the  fact  that  the 
infectious  agents  are  being  vanquished.  In  the  matter 
of  termination,  the  rule  is  not  always  followed;  accord- 
ingly, we  sometimes  find  pneumonia  terminating  by 
lysis,  and  less  often,  typhoid  fever  by  crisis.  One 
curious  exception  to  the  usual  form  that  crisis  takes, 
i.e.,  reduction  in  temperature,  occurs  in  Asiatic  cholera. 
Instead  of  the  temperature  falling,  it  rises  from  below 
normal  (sub-normal)  to  normal  or  above  normal.  The 
characteristic  feature  of  the  crisis  is  thus  reversed,  a 
thing  which  is  associated  with  the  other  reversal  that 
takes  place  in  the  stationary  period  of  cholera,  i.e.,  a 
sub-normal  temperature. 

An  infectious  disease  is  due  to  the  entrance 
Local  and  and  growth  of  infectious  agents,  and  to  the 
General  toxins  (poisons)  which  the  latter  generate. 
Infections.  When  infectious  agents  gain  an  entrance 
into  the  body,  they  act  in  one  of  two  ways, 
namely : 

(i)  Either  they  remain  localized  near  their  portal  of 
entry,  or  in  some  near  or  distant  organ,  during  the 
whole  course  of  the  disease;  or, 

(2)  they  first  establish  a  local  lesion  near  their  portal 
of  entry,  or  in  some  near  or  distant  organ,  and  then, 
from  this  as  a  focus,  invade  the  whole  body. 

The  first  instance  is  descriptive  of  what  is  called  a 
local  injection,  the  second,  of  a  general  injection.     In 


20         INFECTIOUS  AND  PARASITIC  DISEASES. 

both  cases  the  toxins  play  the  same  important  role; 
yet  while  in  the  one  they  are  formed  in  only  one  portion 
of  the  body,  in  the  other,  since  the  infectious  agents 
are  scattered,  they  are  formed  in  all  parts.  Infectious 
diseases  which  result  from  toxins  eliminated  by  micro- 
organisms growing  in  a  circumscribed  area  are  known 
as  toxcemias,  while  those  in  which  the  micro-organisms 
live  and  multiply  in  the  blood-stream  are  called  sep- 
ticcEmias  (in  cases  in  which  bacteria  are  the  invaders, 
bactericemias) .  A  general  infection,  therefore,  corre- 
sponds to  a  septicaemia,  or  bacteriaemia.  It  must  not 
be  inferred,  however,  that  a  toxaemia  always  accom- 
panies a  local  infection,  for  there  are  many  local  infec- 
tions in  which  the  action  of  the  agents  and  their  toxins 
are  purely  local;  the  word  toxaemia  is  reserved  for  local 
infections  associated  with  constitutional  symptoms  of 
poisoning.  To  illustrate :  No  one  would  call  an  abscess 
an  infectious  disease,  although  it  represents  the  localized 
activity  of  certain  bacteria,  and  is  therefore  correctly 
spoken  of  as  a  local  infection.  On  the  other  hand, 
tetanus,  a  constitutional  disease,  has  as  its  local  infection 
a  wound,  frequently  so  trivial,  that  it  has  healed  before 
the  convulsions  begin  which  mark  the  onset  of  this 
terrible  disease.  It  is  the  toxins  formed  by  the  bacilli 
at  one  point,  and  absorbed,  which  give  rise  to  the 
toxaemia. 

A  local,  or  a  general  infection,  may  be  caused  by  either 
a  specific  or  a  non-specific  infectious  agent,  but  not  by 


CAUSES  OF  DISEASE.  21 

any  specific  or  non-specific  agent.  Some  specific 
agents  only  give  rise  to  local  infectious  diseases  (toxae- 
mias), while  others  only  to  septicaemias  (or  bacteriae- 
mias).  Typical  examples  of  toxaemias  due  to  specific 
agents  are  furnished  by  diphtheria,  tetanus  (lock-jaw), 
rabies  (hydrophobia),  and  cholera;  of  septicaemias 
(or  bacteriaemias),  by  anthrax,  typhoid  fever,  relapsing 
fever,  bubonic  plague,  influenza  (La  grippe),  malta 
fever,  etc.  Besides  the  diseases  here  given,  there  are 
many  others  on  the  border-line  between  toxaemias  and 
septicaemias,  that  is  to  say,  the  infection  may  be  local- 
ized, yet  there  is  a  distinct  tendency  for  the  infectious 
agents  to  invade  the  blood.  Such  a  disease  is  pneu- 
monia which,  while  it  is  often  an  infection  localized 
in  the  lungs,  occurs  in  a  form  (croupous)  in  which  the 
pneumococci  which  cause  it  are  found  in  the  blood  in 
about  ninety  per  cent  of  the  cases.  Pulmonary  tuber- 
culosis (consumption)  is  another  case  in  point;  the 
disease  may  remain  localized  in  the  lungs  for  months 
and  even  years,  yet  the  specific  bacilli  often  invade  the 
economy.  When  they  do,  the  germs  are  distributed 
everywhere,  and  a  rapid  termination  of  life  results. 
This  form  of  tuberculosis,  called  by  the  profession 
acute  miliary  tuberculosis,  is  well  known  to  the  laity 
under  the  name  of  rapid,  galloping,  or  quick,  consump- 
tion. 

There  is  another  word  in  current  use  in  medicine 
that  requires  explanation  in  this  place,  viz.,  pyaemia. 


22         INFECTIOUS  AND  PARASITIC  DISEASES. 

By  pycemia  is  understood  an  infection  in  which  the 
micro-organisms  have  estabhshed  suppurating  foci 
in  different  parts  of  the  body.  Where  the  several 
locahzations  have  had  their  origin  in  another,  single 
focus,  the  former  are  often,  although  erroneously,  spoken 
of  as  metastatic  abscesses. 

Heretofore  the  course  of  a  disease  due  to 
Combined  only  one  infectious  agent  has  been  described , 
Infections,     and  while  we  usually,   in  acute  disease, 

are  dealing  with  a  single  or  uncombined 
infection,  the  opposite,  mixed  or  combined  infections, 
are  not  uncommon.  Thus  occur  together  measles 
and  scarlet  fever,  measles  and  whooping-cough,  scarlet 
fever  and  diphtheria,  typhoid  fever  and  pneumonia, 
etc.  When  two  infections  occur  in  the  same  individual, 
the  symptoms  of  one  disease  are  likely  to  be  masked  or 
held  in  abeyance  by  those  of  the  other,  the  extent  to 
which  this  takes  place  depending  upon  whether  they 
develop  simultaneously  or  in  succession.  It  also 
depends  upon  the  nature  of  the  diseases.  Thus  pneu- 
monia for  a  number  of  days  may  run  so  typical  a  course 
in  a  person  suffering  from  consumption  as  to  deceive 
the  ablest  clinician  into  believing  that  only  one  disease, 
pneumonia,  exists.  On  the  other  hand,  pneumonia  in 
the  alcoholic,  in  the  sufferer  from  some  chronic  dis- 
order, e.g.,  Bright's  disease,  diabetes,  chronic  heart 
disease,  or  coming  on  during  the  course  of  an  acute 
infection,  may  be  entirely  overlooked  in  spite  of  the 


CAUSES  OF  DISEASE.  23 

fact  that  it  is  known  to  be  the  most  frequent  direct 
cause  of  death. 

However,  two  infections  may  concurrently  run 
typical  courses  in  the  same  individual.  This  happens 
when  scarlet  fever  and  measles  develop  simultaneously. 

When  an  infectious  agent  attacks  an 
Secondary  individual  who  is  already  suffering  from 
Infection.      the  attacks  of  another,  we  speak  of  the 

former  as  a  secondary  injection.  Most 
secondary  infections  follow  as  a  result  of  the  diminution 
in  vital  resistance  consequent  upon  the  first  infection. 
Apart  from  the  ordinary  diseases  of  childhood,  there 
are  two  notable  infections  that  are  very  commonly 
secondary,  because  they  take  advantage  of  any  depres- 
sion in  vital  resistance  that  the  body  has  suffered. 
Their  frequency  and  permiscuity  are  so  well  established, 
that  every  precaution  should  always  be  taken  to  guard 
a  patient  from  their  attack.  Reference  is  made  to 
tuberculosis  and  pneumonia.  The  micro-organisms 
which  cause  these  two  diseases  lead  all  others  as  second- 
ary invaders  of  the  body,  and  undoubtedly  cause  a 
larger  number  of  deaths  than  all  the  diseases  combined 
to  which  they  are  secondary.  Next  to  the  tubercle 
bacillus  and  the  pneumococcus  in  point  of  frequency 
as  secondary  invaders  come  the  common  pyogenic 
or  pus-producing  bacteria,  among  which,  it  should 
always  be  remembered,  is  included  the  microbe  of 
erysipelas. 


24         INFECTIOUS  AND  PARASITIC  DISEASES. 

An  interesting  and  important  phenomenon 

Infectious     concerning  the  infectious  diseases  is  their 

self-limitinsj    nature.     Clinical     evidence 

ARE  Self-  ^  ^  ^  ^  1  .  -      ,   . 

LIMITING  abundantly  corroborates  the  verity  of  this 
statement,  since  treated  or  untreated, 
every  infectious  disease  follows,  as  it  were,  a  prescribed 
course.  The  fact  that  we  divide  this  course  into  periods 
is  a  significant  admission.  Except  in  the  case  of  a 
few  diseases,  for  which  we  have  specifics,  the  progress 
and  termination  of  an  infectious  disease  is  determined 
well-nigh  entirely  by  the  reactionary  or  fighting  powers 
of  the  body.  All  living  things  struggle  for  existence, 
which  is  only  another  way  of  saying  they  resist  de- 
struction. The  efforts  that  an  organism  puts  forth  to 
survive  is  an  inherent  quality  that  it  can  no  more 
control  than  it  can  its  birth.  Therefore,  when  the  body 
is  attacked  by  an  infectious  agent,  it  sustains  the  attack 
with  such  weapons  as  nature,  through  heredity,  has 
supplied  it  for  this  very  purpose;  and  to  this  fact,  that 
nature  is  by  far  the  greatest  healer,  all  physicians  and 
nurses  cannot  fail  to  testify. 

In  the  sense  in  which  self-limiting  is  used  when  refer- 
ring to  infectious  diseases,  there  is,  therefore,  imphed 
the  meaning  that  the  body  delimits  the  period  of  disease 
irrespective  of  medication.  It  may  seem  to  aspiring 
novices  in  medicine  a  sad  admission,  and  one  that  may 
cause  them  deep  disappointment,  yet  it  cannot  be 
denied    that    infectious    diseases    tend   to    spontaneous 


CAUSES  OF  DISEASE.  25 

recovery.     This  curious  fact  is  the  result  of  natural 
phenomena. 

Animal  experiments  have  taught  us  that 
when  certain  substances  injurious  to  the 
Antibodies,  well-being  of  an  animal  are  introduced 
into  the  blood,  other  substances  are  formed 
which  have  the  power  of  neutralizing 
further  injections  of  the  first.  Substances  manufac- 
tured by  a  living  organism  in  this  way  are  technically 
called  "antibodies;"  and  the  antitoxins  of  commerce, 
which  are  prepared  from  living  animals  by  inoculating 
them  with  the  toxins  (poisons)  of  various  diseases 
belong  to  this  class.  Antibodies  are  formed  in  an  animal 
only  when  the  substances  which  give  rise  to  them 
have  destroyed  a  certain  amount  of  tissue,  the  injured 
tissues  supplying  the  stimulants  w^hich  incite  to  activity 
the  protective  functions  of  the  body.  When  produced, 
antibodies  have  no  beneficial  effects  whatsoever  upon 
the  tissues  already  destroyed,  but  act  simply  either  to 
neutralize  any  additional  toxin  which  may  yet  be 
circulating,  or  which  may  get  into  the  body  from  the 
exterior  at  another  time.  For  these  reasons  antitoxins 
are  intrinsically  prophylactic^  rather  than  curative,  in  as 
much  as  if  inoculated  into  a  healthy  person,  they  guard 
against  disease  by  preventing  tissue  destruction ;  whereas 
after  infection,  they  safe-guard  the  body  from  greater 
injury  than  has  already  occurred  by  neutralizing  any 
circulating  poison.     It  is  this  latter  action  which  has 


26         INFECTIOUS  AND  PARASITIC  DISEASES. 

given  them  their  reputation  as  curative  principles. 
The  production  of  antibodies  represents  the  reactionary 
or  fighting  powers  of  the  body  above  referred  to,  and 
is  its  natural  weapon  of  defense  against  disease. 

As  the  result  of  bacterial  infections,  distinctly  differ- 
ent antibodies  are  formed  which  owe  their  origin  to 
peculiarities  in  attack  of  the  infecting  agents.  All 
bacteria  produce  disease  through  their  toxins,  but 
because  the  manner  in  which  the  latter  are  eliminated 
is  not  the  same  for  all,  there  arise  differences  both  in  the 
nature  of  the  protective  substances,  and  the  manner  in 
which  these  substances  protect.  From  the  standpoint 
of  disease-production  bacteria  may  be  divided  in  a 
broad  way  into  two  classes,  viz.,  (i)  those  that  attack 
the  body  rather  through  a  diffusible  poison,  which  they 
excrete,  than  by  enormous  reproduction;  and  (2)  those 
in  which  multiplication  is  the  primary  or  essential 
phenomenon,  toxin-excretion  subsidiary.  Bacteria  of 
the  first  order,  through  their  toxins,  give  rise  to  sub- 
stances which  neutralize  the  latter,  that  is,  antitoxins. 
Bacteria  of  the  second  order,  contrariwise,  stimulate  the 
body  to  the  formation  of  substances  antagonistic  to 
the  bacteria  themselves,  i.e.,  antibacterial  or  bacteri- 
cidal substances.  The  protection  that  antibodies  which 
are  bactericidal  furnish  the  body  comes  through  their 
power  of  dissolving  the  bacteria  which  cause  the 
disease.  If  immunity  against  infection  is,  therefore, 
contrasted  from  the  standpoint  of  the  etiological  agents, 


CAUSES  OF  DISEASE.  27 

it  is  either  antitoxic  or  bactericidal.  Technically  bacteri- 
cidal antibodies  are  known  as  lysins,  or  bacteriolysins. 
Antedating  and  also  accompanying  the 
Agglutinins,  formation  of  the  solvent  antibodies  (bac- 
teriolysins), there  appears  in  the  blood- 
serum  of  infected  animals  and  persons  other  antibodies 
which  have  the  property  of  drawing  together  in  groups 
or  clumps  the  invading  bacteria.  This  phenomenon 
is  called  agglutination ,  the  substances  which  excite 
it,  agglutinins. 

Agglutination,  it  is  commonly  accepted,  has  these 
two  advantages :  It  is  a  preliminary  stage  in  the  process 
of  immunity  (it  appears  before  the  bacteriolytic  sub- 
stance); it  facilitates  the  ingestion  of  the  bacteria  by 
the  phagocytes  (phagocytosis). 

Bacteriolysins  and  agglutinins  are  specific  substances, 
just  as  antitoxins  are,  and  therefore  act  only  when 
brought  into  relation  with  such  bacteria  as  call  them 
forth.  This  knowledge  of  the  specificity  of  the  agglu- 
tinins is  made  use  of  for  the  diagnosis  of  various 
diseases,  especially  typhoid  fever,  the  examination  for 
agglutination  in  the  latter  disease  constituting  the  well- 
known  Widal  reaction. 

In   recovery  or   immunity  from   diseases 

Opsonins,    due  to  the  second  class  of  bacteria,  i.e., 

those  which  attack  the  body  largely  through 

multiplication,   another  antibody  has  lately  come  to 

the  fore  which  bids  fair  to  overshadow  all  others  in 


28         INFECTIOUS  AND  PARASITIC  DISEASES. 

importance.  This  is  a  bactericidal  antibody,  opsonin 
(I  prepare  a  meal  for),  that  acts  in  conjunction  with  the 
leucocytes  to  rid  the  body  of  invading  bacteria. 

Opsonin  is  normally  found  in  the  blood,  and  is 
increased  in  immunity.  It  acts  in  such  a  way  upon 
infectious  agents  that  they  not  only  strongly  attract  the 
phagocytic  leucocytes  (positive  chemotaxis),  but  makes 
them  easier  of  digestion  by  the  latter.  It  is  well  that 
the  associated  action  of  opsonin  and  phagocytosis 
has  been  discovered,  for  bacteriologists  had  well-nigh 
despaired  of  producing  bactericidal  serums  comparable 
in  potency  to  diphtheria  and  tetanus  antitoxins;  the 
latter,  once  their  toxins  were  separated  from  the  bac- 
teria, were  comparatively  easy  to  prepare;  but  in  the 
case  of  those  bacteria  in  which  little  or  no  diffusible 
poison  is  secreted,  the  problem  of  making  immune 
serums  presented  insurmountable  difficulties.  This 
is  the  reason  that  in  a  long  list  of  diseases,  such  as 
typhoid  fever,  bubonic  plague,  Asiatic  cholera,  bacillary 
dysentery,  etc.,  immune  serums  have  not  been  forth- 
coming. In  opsonin,  however,  we  have  a  force  to 
work  with  which,  it  would  appear,  can  be  increased 
at  will,  so  that  if  the  expectations  of  workers  with 
opsonins  are  realized,  it  will  not  be  long  before  the 
immunization  and  cure  of  the  above  mentioned  mala- 
dies will  be  in  our  hands. 

It  is  now  almost  twenty  years  since  Metchnikoff 
first  called  attention  to  the  part  that  certain  white 


CAUSES  OF  DISEASE.  29 

cells  in  the  blood  take  in  both  the  prevention  and  cure 
of  infections.  These  cells  (leucocytes),  which  he 
called  phagocytes,  he  believed  acted  through  their 
power  of  taking  up  and  digesting  bacteria.  During 
all  these  years  since  the  publication  of  his  theory  of 
phagocytosis  Metchnikoff  has  added  many  valuable 
facts  corroborating  his  views.  In  the  light  of  the 
recently  discovered  antibody,  opsonin,  his  views  on 
the  protective  function  of  the  leucocytes  are  strongly 
supported,  in  that  data  for  the  first  time  is  supplied 
which  explains  the  conditions  under  which  phagocy- 
tosis is  active.  Opsonin  in  the  blood-serum  of  immune 
animals  and  persons  sensitizes  or  opsonizes  the  injec- 
tions agents  for  easier  destruction  by  the  phagocytes. 

Injuries  to  tissues  per  se  produce  symptoms,  through 
the  disturbance  of  functions  which  such  loss  to  the 
economy  entails;  but  besides  these  symptoms,  there 
are  others,  in  every  infectious  disease,  which  can  be 
definitely  ascribed  to  the  production  of  the  defensive 
substances.  The  phenomena  of  disease,  therefore, 
are  of  a  composite  character,  comprising  both  the 
symptoms  of  injury  and  those  of  defense.  What  part 
of  the  symptoms  each  of  these  factors  causes  in  a  case, 
it  is  impossible  to  determine,  but  of  this  we  may  always 
feel  sure  (because  the  experimental  proofs  in  its  favor 
are  conclusive)  no  insignificant  part  of  the  fever  and 
general  malaise  in  every  infectious  disease  is  a  necessary 
adjunct  to  antibody  production.     This  fact  lends  the 


30         INFECTIOUS  AND  PARASITIC  DISEASES. 

strongest  support  to  the  view,  formerly  much  debated, 
that  fever  is  a  benign  and  necessary  feature  in  the  class 
of  diseases  we  are  discussing.     The  modern  concep 
tion  of  disease  takes  the  position  that  recovery  fror 
an  infection  is  always  brought  about  either  through  th 
production  of  an  immunizing  substance  by  the  bod} 
or  through  the  introduction  of  the  same  from  without. 
In  the  body,  the  period  of  invasion  marks  the  beginning 
of  antibody  formation,  which  from  this  time  goes  on 
until  either  recovery  or  death  supervenes.    If  the  former, 
sufficient  antibody  is  formed  to  equalize  the  bacteria 
or  their  poisons  and  prevent  further  inroads  of  either 
upon  the  tissues;  if  the  latter,  the  body's  defensive 
mechanism  fails  to  act  through  weakness,  or  is  over- 
come by  the  intensity  and  massiveness  of  the  virus. 
The  use  of  antitoxin  in  disease  marks  the  highest  refine- 
ment of  specific  medication,  in  that  an  immunizing  sub- 
stance is  injected  into  a  patient  which  can  be  depended- 
upon  to  counteract  or  neutralize  a  definite  poisonous- 
(toxic)  substance.     It  aims  to  take  from  the  patient 
the  burden  of  producing  antibodies,  which  at  best  is 
slow  and  too  often  a  doubtful  quality,  by  injecting 
them  fully  formed  and  active.     These  have  been  pre- 
pared from  some  animal  which  has  been  subjected  to 
the  poison  and  has  recovered.     In  other  words,  the 
immunity  forced  upon  an  animal  is  transferred  to  the 
patient.    From  what  has   been   said   concerning  the 
action  of  antibodies  in  that  they  only  neutralize  their 


CAUSES  OF  DISEASE.  31 

opposites,  it  is  obvious  that  the  earher  they  are  used, 
he  more  beneficial  and  potent  will  they  prove  in  treat- 
ig  disease.  It  is  their  late  use  after  great  tissue  de- 
riTuction  has  occurred,  that  is  responsible  for  failure. 
'41  an  immune  person  or  animal,  antibodies  are  found 
troughout  the  body,  in  largest  quantity  in  the  blood. 
And  it  is  such  blood-serum,  separated  from  the  other 
elements  of  the  blood,  which  is  the  antitoxin  of  world- 
wide fame.  Antitoxin  (antibody)  not  only  causes  no 
reactions  when  injected  into  a  patient — the  animal 
from  which  it  was  obtained  suffered  these — but  it 
causes  the  symptoms  due  to  the  body's  efforts  to  produce 
it  on  its  own  account  to  at  once  abate.  Moreover,  if 
an  amount  sufficient  to  neutralize  all  floating  poison  is 
injected,  the  symptoms  due  to  the  action  of  this  are 
also  eliminated.  Therefore,  there  only  remain  such 
disturbances  as  are  inevitable  when  tissues  are  destroyed 
and  must  needs  be  re-formed.  And  here  again  are  seen 
.ne  wonderful  workings  of  nature.  In  those  diseases 
for  which  we  have  specifics,  the  body-forces  play  just 
as  important  a  role  as  the  specifics;  specifics  neutralize 
the  bacteria  and  their  toxins,  but  they  cannot  restore 
to  normal  the  tissues  which  these  agents  have  injured, 
nor  the  functions  of  organs  which  they  have  im- 
paired. Repair  is  a  function  of  the  organism  which 
may  be  assisted  but  never  supplanted.  The  part 
played  by  the  body  in  this  respect  in  infectious  diseases 
is  analogous  to  that  which  it  plays  in  surgery.     The 


32         INFECTIOUS  AND  PARASITIC  DISEASES. 

surgeon,  in  operating  for  the  removal  of  malignant 
tumors  or  for  some  other  urgent  cause,  does  his  utmost 
when  the  dangerous  condition  for  which  he  operates 
is  removed.  But  how  much  would  his  surgery  avail, 
if  the  body  did  not  potentially  possess  amazing  powers 
for  repair  and  reconstruction?* 

Nearly  all  complications  occurring  in  the 
course  of  diseases,  whether  they  be  infec- 

TIONS.  .     r         •  1 

tious  or  non-mfectious,  are  due  to  mfec- 
tious  agents;  and  the  infectious  agents  principally  at 
fault  are  bacteria.  The  source  of  the  infecting  bacteria 
depends  upon  circumstance.  It  may  happen  that  the 
agent  has  its  habitat  upon  the  individual's  integument, 
or  within  a  cavity  of  the  body  leading  to  the  exterior. 
Thus,  pneumonia,  occurring  as  a  complication,  is 
caused  by  the  pneumococcus,  a  micro-organism  that 
almost  everyone  harbors  in  his  mouth  even  in  health. 
An  instance  of  contamination  from  the  integument  is 
afforded  by  furunculosis  (boils),  a  common  sequel  to 
various  infections  during  or  after  convalescence  is 
established. 

A  second  source  for  bacteria  which  complicate 
disease,  is  found  in  objects,  insects,  and  persons  that 
come  in  contact  with  the  patient.  Thus  wounds 
soiled  with  earth  are  those  in  which  tetanus  (lock-jaw), 
and  gaseous  gangrene,  are  liable  to  develop,  because 
the  bacteria  which  bring  about  these  infections  have 

*  See  Chapter  on  Inflammation. 


CAUSES  OF  DISEASE.  33 

their  home  in  the  ground.     The  bacteria  that  produce 
pus  (pyogenic  bacteria)  are  also  found  in  the  ground. 

Insects,  such  as  flies,  bed-bugs,  mosquitoes,  etc., 
may  be  the  means  of  conveying  infections.  Finally, 
persons  may  convey  infections.  Among  persons  con- 
veying infections,  physicians  and  nurses  are  especially 
dangerous  on  account  of  the  frequent  and  close  contact 
that  they  have  with  the  sick. 

The  manner  in  which  complications  have  heretofore 
been  spoken  of  places  them  in  the  same  category  with 
secondary  infections.  This  conception  of  them,  how- 
ever, requires  qualification.  Besides  resulting  from 
invasion  of  the  body  by  bacteria  other  than  the  one 
producing  the  original  infection,  complications  may  be 
due  to  another  localization  in  a  distant  part  of  the  body 
of  the  same  organism  that  produced  the  original  infec- 
tion. Under  such  circumstances  we  do  not  speak  of 
the  complication  as  a  secondary  infection,  but  a  second- 
ary localization  or  metastasis.  Ignorance  of  the  nature  of 
infectious  agents  and  their  migratory  tendency  led,  in  the 
past,  to  such  names  as  typhoid-pneumonia,  a  designation 
which  is  no  longer  countenanced  because  we  know  that 
this  disease,  even  when  the  pneumonia  accompanies  or 
initiates  typhoid,  is  typhoid  fever  with  pulmonary  locali- 
zation of  the  typhoid  bacillus  in  the  lungs.  Misconcep- 
tions concerning  their  origin  were  likewise  responsible 
for  such  names  as  typho-malarial  fever,  diphtheritic 
tonsillitis,  etc.,  hybrids  for  which  there  is  no  excuse. 
3 


34         INFECTIOUS  AND  PARASITIC  DISEASES. 

In  the  course  of  all  chronic  diseases  of 
Terminal  v/hatever  nature,  the  sufferer  is  particularly 
Infections,  prone  to  have  his  original  disease  com- 
plicated by  some  infection.  Indeed,  it  is 
the  latter  that  is  the  common  cause  of  death.  Pneu- 
monia heads  the  list  as  a  secondary  invader,  and  also 
in  bringing  about  a  termination  of  life.  Next  in  point 
of  frequency  is  tuberculosis,  and  third,  are  pyogenic 
infections.  When  secondary  infections,  or  complica- 
tions, kill,  they  are  spoken  of  as  terminal  injections. 
Whether  the  body  ever  returns  to  a  normal 
Evolution  state  after  having  recovered  from  an  infec 
OF  Disease,  tious  disease  is  still  an  open  question.  In 
the  large  majority  of  cases,  it  apparently 
does,  but  we  must  always  remember  that  time,  only, 
can  answer  this  question  in  any  individual  case. 
Certainly  a  "spell"  of  any  one  of  the  infectious  diseases 
is  not  regarded  by  the  profession  as  interfering  with 
the  usual  expectancy.*  Nevertheless,  as  the  years  go 
by,  we  are  laying  more  and  more  stress  upon  past 
illness  as  a  factor  in  present  disorders. 

For  the  most  part,  "diseases  that  owe  their  origin 
to  past  illness  are  affections  of  organs,"  e.g.,  Bright's 
disease,  chronic  heart  disease,  locomotor  ataxia,  the 
organs  being  involved  in  the  infectious  process  at  the 
time  of  the  acute  infection,  and  apparently  subsiding 

♦Expectancy — the  mean  or  average  duration  of  life  of  individuals 
after  any  specified  age. 


CAUSES  OF  DISEASE.  35 

with  it.     We  say  apparently  advisedly,  because,  although 
the   acute   inflammation  subsides,   it  too  often  gives 
place   to   a   chronic   inflammation   that   extends  over 
years.     This  chronic  inflammatory  state  is  no  longer 
dependent  in  most  cases  upon  the  infectious  principle 
which  caused  the  initial  lesion,  but  is  a  slow  sclerosis, 
or  cicatrization,  which  consists  in  a  gradual  contraction 
and  substitution  of  the  normal  tissues  of  a  part  by  scar 
tissue.     The  change  is  especially  prone  to  occur  in 
organs  that  have  sustained  an  injury  of  one  kind  or 
another,  and  is  really  a  vicarious  evolution  that  the 
tissues  are  subject  to.     There  is  a  danger  in  the  new 
condition  that  arises  both  from  the  contractions,  and 
the  loss  in  organic  cellular  constituents,  since  in  the 
one  case  functions   are  interfered  with,  in  the  other, 
metabolism*    is    disturbed.     The    seriousness    of    the 
lesion  depends  upon  the  organ  in  which  the  original 
injury  was  located,   and  its  importance  to  the  vital 
processes  of  the  body.     One  or  two  illustrations  will 
suffice  to  elucidate  our  point.     A  person  has  typhoid 
fever  and  apparently  makes  a  complete  recovery.     Ten, 
fifteen  or  twenty  years  afterwards  he  seeks  medical 
advice  for  shortness  of  breath  and  cough.     His  case 
is  diagnosed  as  chronic  heart  disease.     Whence  came 
the  lesion  of  his  heart  valves  ?    When  closely  questioned, 
he  may  remember  that  the  physician  who  attended 

*  Metabolism— chemical   change   within  the  body  m  nutrition  and 
secretion. 


36         INFECTIOUS  AND  PARASITIC  DISEASES. 

him  at  the  time  of  his  fever  did  remark  that  there  was 
some  shght  evidence  of  cardiac  injury.  But  even  this 
evidence  of  the  connection  between  his  present  trouble 
and  the  earlier  typhoid  fever  is  now  no  longer  necessary ; 
we  have  learned  through  experience  the  connection. 
Are  typhoid  bacilli  causing  the  present  trouble  ?  Assur- 
edly not !  The  original  cause  was  an  inflammation  of  the 
heart  valves  from  the  typhoid  bacilli,  most  likely,  or 
some  other  microbe  that  gained  an  entrance  into  the 
blood  during  his  attack  of  typhoid.  The  lesion  of 
the  heart,  to  all  appearances,  healed.  But  a  cicatrix 
remained,  that,  according  to  the  manner  of  all  cica- 
trices, continued  to  contract,  until  through  the  disability 
it  produced  in  the  functioning  of  the  heart,  gave  rise  to 
symptoms.  Substantially  the  same  history  is  obtained 
in  many  cases  of  Bright's  disease  (chronic  nephritis), 
the  antecedent  disease  being  either  scarlet  fever, 
measles,  diphtheria,  or  typhoid  fever. 

We  have  used  the  word  infectious  a  number  of  times, 
but  purposely  have  avoided  using  another  word, 
namely,  contagious^  on  account  of  the  many  loose  inter- 
pretations that  are  given  it.  To  us  it  seems  best  to 
speak  of  a  contagion,  or  a  contagious  disease,  only 
when  the  microbe  is  readily  communicable  from  person 
to  person  by  mediate  or  immediate  contact.  The 
term  should  be  used  as  descriptive  of  a  quality  of  the 
germ  or  of  a  microbic  disease.  It  should  not  be  used 
synonymously  with  infectious  or  infection;  in  fact,  if 


CAUSES  OF  DISEASE.  37 

the  words  were  synonymous,  we  would  scarcely  describe 
a  disease,  such  as  diphtheria,  as  being  both  infectious 
and  contagious.  A  disease  may  be  contagious,  or  it 
may  be  infectious;  or  it  may  be  both  contagious  and 
infectious.  Malaria  is  an  infectious  disease,  but  not 
contagious;  scabies  (itch)  is  contagious  but  not  infec- 
tious; diphtheria  is  both  contagious  and  infectious. 
Diseases  exhibit  at  times,  however,  marked  differences 
in  regard  to  these  characteristics.  Sometimes  an  infec- 
tious disease  not  ordinarily  contagious  may,  in  some 
manner  as  yet  not  understood,  become  contagious. 
This  happens  in  pneumonia,  which  under  such  cir- 
cumstances partakes  of  the  characteristics  of  an  epi- 
demic disease. 

Of  late  years  it  has  seemed  best  to  some 

authors,    on    account    of    the    indifferent 

CABLE.  ' .        ,  .  ,     ,  ,     .    .      .  , 

manner  m  which  the  words  mfectious  and 

contagious  have  been  used  in  describing  a  disease,  to 
omit  them  entirely,  and  in  their  stead  to  speak  of  these 
diseases  as  coimnimicahle.  This  seems  an  excellent 
innovation  because  only  diseases  caused  by  living  things 
are,  strictly  speaking,  communicable.  An  objection 
might  be  made  to  the  term  because  it  would  include 
parasitic  affections,  but  this  cannot  for  long  have  any 
real  force ;  it  is  difficult  at  best  to  draw  a  nice  distinction 
between  many  diseases  due  to  parasites  and  the  infec- 
tious agents,  and  we  might  just  as  well  for  good  have 
a  word  adaptable  and  usable  for  both. 


CHAPTER  II. 
BACTERIOLOGY. 

Bacteria  (sing.,  bacterium)  are  low  forms  of  life 
that  are  generally  conceded  to  belong  to  the  vegetable 
kingdom.  They  resemble  the  moulds  in  many  ways; 
in  fact,  one  name  for  them  is  fission-moulds,  a  term 
derived  from  the  circumstance  that  multiplication  of 
the  individual  bacterium  takes  place  by  simple  division 
of  the  whole  organism  into  two  parts.  They  further 
resemble  the  moulds  in  not  possessing  chlorophyl,  the 
green  coloring  matter  by  virtue  of  which  in  the  pres- 
ence of  sunlight,  plants  are  enabled  to  decompose 
carbon  dioxide  and  ammonia,  and  use  their  constituents 
for  food. 

The  absence  of  chlorophyl  in  bacteria  necessitates 
some  form  of  proteid  as  food,  whence  results  the  phenom- 
enon of  the  lowest  forms  of  life  consuming  the  same 
kinds  of  food  as  the  higher  animals. 

Bacteria  live  chiefly  upon  the  remains  of  animals  and 
plants,  to  a  lesser  extent  upon  living  forms  of  both 
kingdoms.  But  whilst  they  share  a  common  food 
with  animals,  the  disintegrations  which  they  work  in  it 

38 


BACTERIOLOGY.  39 

result  in  simpler  and  more  important  end-products. 
These  consist  of  the  gases  absolutely  essential  to  plant 
life,  namely,  carbon  dioxide  (CO2)  and  ammonia 
(NH3).     A  third  end-product  is  water  (H^O). 

The  amount  of  carbon  dioxide  produced  by  animals 
out  of  starches  and  sugars  is  insignificant  in  comparison 
with  the  needs  of  the  vegetable  kingdom,  and  were  there 
no  other  source  for  this  important  food  element,  the 
plant  world  would  either  suffer  a  great  deficit  or  be 
restricted  in  its  growth.  The  same  is  true  of  nitrogen, 
another  important  constituent  of  plants,  and  required 
by  them  in  an  easily  assimilable  form,  such  as  ammonia 
(NH3).  It  is  the  peculiar  office  of  bacteria  to  supply 
plants  with  the  largest  amounts  of  both  of  these  constit- 
uents. On  this  account  they  are  the  natural  inter- 
mediaries between  plants  and  animals  in  point  of  food 
production,  playing  by  far  the  most  important  part  in 
the  economy  of  nature.  Without  bacteria,  plant-life 
would  be  scanty  or  entirely  wanting;  and  since  the 
animal  kingdom  depends  upon  plants  for  existence, 
there  would  result  a  world  lacking  in  every  form  of 
higher  animal  life. 

The  part  that  bacteria  play  as  scavengers 
Arts  and  of  the  earth  and  providers  of  food  for 
Industries,     plant-life,  only  displays  a  limited  side  of 

their  usefulness.  In  the  arts  and  industries 
they  are  as  essential  to  modern  economic  life  as  are  the 
ingenious  mechanical  inventions  of  man.     Many  secret 


40         INFECTIOUS  AND  PARASITIC  DISEASES. 

processes  now  in  use  in  the  arts  and  manufactures 
are  but  devices  to  harness  these  natural  forces.  Thus 
in  the  manufacture  of  hnen,  hemp  and  sponges,  in  the 
butter,  cheese,  and  vinegar  industries,  in  tobacco- 
curing,  etc.,  bacteria  play  the  important  role. 

Curiously,  in  the  popular  mind,  bacteria 
Saprophytes,  are  only  associated  with  disease,  and  are 

regarded  with  abhorrence  on  that  account ; 
yet  of  the  untold  hundreds  of  species,  only  about  forty 
are  known  to  produce  disease  in  human  beings. 

Bacteria  which  are  useful  to  mankind  in  so  many 
ways  belong  to  the  class  of  organisms  known  as  obligate 
saprophytes,  i.e.,  "an  organism  that  lives  upon  dead 
organic  matter."  Bacteria  that  produce  disease,  on 
the  other  hand,  belong  to  the  parasites  and  infectious 
agents,  a  description  of  which  has  already  been  given 
in  the  preceding  chapter.  However,  the  ability  of  a 
bacterium  to  live  upon  dead  organic  matter  does  not 
determine  its  status  from  the  standpoint  of  the  produc- 
tion of  disease.  The  obligate  saprophytes,  as  their 
name  imphes,  are  restricted  to  a  diet  of  dead  things; 
but  the  parasitic  bacteria,  while  preferably  parasitic 
in  their  habits,  may  nevertheless  lead  a  saprophytic 
existence.  Siich  species  are  known  as  jacultative 
saprophytes.  Most  of  the  disease-causing  bacteria 
belong  to  this  class,  a  factor  that  has  proven  of  incal- 
culable value  in  studying  them.  Indeed,  bacteriology 
dates  its  rapid  progress  from  the  time  that  pathogenic 


BACTERIOLOGY.  41 

bacteria  were  first  grown  upon  an  artificial  pabulum  in 
the  laboratory.  The  adaptability  of  bacteria  to  various 
kinds  of  foods  explains  the  spread  of  many  diseases  by 
foods  and  water,  and  also  the  tenacity  that  certain 
diseases  display  in  clinging  to  a  house  or  to  clothing. 
Almost  everywhere  there  are  small  amounts  of  organic 
matter  and  moisture,  and  these  microscopic  forms 
of  life  which  we  are  considering  require  such  infini- 
tesimal amounts  of  either,  that  it  is  possible  for  them 
to  live  where  nothing  else  can. 

Harmful  bacteria,  that  is,  those  that  are 
ATHOGENic    (.g^p^^g  ^f  producinff  disease,  are  called 
AND  NON-  ^,  .       ,  ,  .     . 

PATHOGENIC    pc^^hogemc;  harmless  varieties,  or  sapro- 

Bacteria.  phytes,  are  called  non- pathogenic.  A 
pathogenic  bacterium,  however,  cannot 
always  produce  disease  when  it  finds  lodgment  within 
the  body.  This  special  characteristic  is  extraordinarily 
variable,  appearing  and  disappearing  under  a  variety 
of  circumstances.  Pathogenicity  in  a  bacterium  depends 
upon  its  power  to  produce  toxins  (poisons),  a  function 
which  is  extremely  susceptible  of  loss  by  exposure 
to  many  natural  agencies.  A  pathogenic  bacterium 
that  can  produce  its  specific  toxins,  and  therefore  bring 
about  disease,  is  spoken  of  as  virulent^  one  that  cannot, 
as*  non-virulent.  For  the  foregoing  reasons  we  recognize 
in  all  pathogenic  bacteria  both  varieties.  However, 
virulence  and  non-virulence  are  evanescent  qualities, 
requiring  only  alterations  in  environment  to  be  made 


42         INFECTIOUS  AND  PARASITIC  DISEASES. 

to  appear  and  disappear.  What  the  circumstances 
are  that  lead  to  this  change  will  be  explained  in  the 
third  and  fourth  chapters. 

In  size   bacteria  are   the  smallest  living 
Size.         things  that  we  can  see  with  the  modern 

microscope.  In  masses  they  are  readily 
seen  with  the  unaided  eye  as  moist,  slimy,  or  dry  films 
floating  upon  the  surface  of  foul  fluids  or  water,  or 
covering  decomposing  animal  or  vegetable  matter. 
Some  of  them  produce  beautiful  colors;  others  have  the 
peculiar  property  of  producing  phosphorescence;  still 
others  cause  the  stench  of  decomposition. 

Bacteria  vary  in  size  between  five-tenths  of  a  micro- 
millimeter  and  twenty  to  forty  micro-millimeters,  and 
as  a  micro-millimeter  is  the  one-thousandth  part  of  a 
millimeter  (about  one-twenty-five-thousandth  of  an 
inch),  only  a  vague  conception  of  their  minuteness  can 
be  formed  unless  one  has  had  experience  in  working 
with  microscopic  forms  of  life. 

What  bacteria  lack  in  size  they  make  up 

in    the    astonishinoj    capacity    that    they 

CATION.  '^  .    .     , .  .  -r-        1 

possess  of  rapid  multiplication.  Each 
bacterium  consists  of  a  single  cell  only  (unicellular), 
which  under  favorable  circumstances  produces  count- 
less other  cells.  This  is  accomplished  by  simple 
division  (fission)  of  the  whole  cell  body.  The  two 
individuals  formed  out  of  the  first  one,  begin  dividing 
into  four  before  complete  separation  has  taken  place; 


BACTERIOLOGY.  43 

the  four  divide  into  eight,  the  eight  into  sixteen,  the 
sixteen  into  thirty-two.  Since  it  takes  only  thirty 
minutes  for  one  cell  to  divide,  it  can  be  computed 
approximately  how  many  new  individuals  will  be 
formed  in  twenty-four  hours  out  of  a  single  bacterium. 
Conn  gives  the  number  as  ''over  16,500,000  in  one 
day,  and  about  281,500,000  in  two  days.  In  three 
days,  at  this  rate  of  multiplication  they  would  produce 
a  mass  of  bacteria  weighing  16,000,000  pounds." 
However,  these  figures  have  no  practical  significance, 
and  are  given  merely  to  convey  to  the  reader  some  con- 
ception of  their  astonishing  rate  of  multiplication.  In 
nature  multiplication  is  rapid,  as  may  be  inferred  from 
the  great  changes  they  work,  but  their  activities  are 
limited  to  their  usefulness.  Their  growth  is  held  in 
check  by  the  products  of  their  own  metabolism  (excre- 
tory products),  by  the  absence  of  suitable  food,  and  by 
natural  forces  acting  upon  them  as  they  do  upon  all 
creation. 

When  examined  with  a  microscope,  indi- 
Shape.       vidual  bacteria  are  seen  to  look  like  so 

many  dots,  dashes,  and  commas.  There 
are  thousands  of  species  of  bacteria,  yet  each  species 
conforms  more  or  less  closely  to  one  of  these  three 
shapes.  According  to  their  form,  therefore,  they  are 
called,  cocci,  bacilli,  and  spirilla,  and  under  these 
designations  all  known  species  are  classified. 


44         INFECTIOUS  AND  PARASITIC  DISEASES. 

To  the  cocci,  or  micrococci  (sing.,  coccus) — belong 
the  dots  or  spherical  forms. 

Fig.  I. — Staphylococci.  Streptococci.  Diplococci.   Tetrads.     Sarcinae. 
^  .    :  '^  ■    (Williams.) 

To   the   bacilli    (sing.,   bacillus) — the    dash-like   or 
rod-shaped  bacteria;  and  to  the 


» 


Vi 


Fig.  2. — Bacilli  of  Various  Forms.     (Williams.) 


Spirilla  (sing.,  spirillum) — the  spiral,  corkscrew,  or 
comma-shaped  forms. 


>  V  4/ 


Fig.  3.— Spirilli  of  Various  Forms.    (Williams.) 

Certain  of  the  bacteria  exhibit  a  singular 
Grouping.       arrangement  to  each  other,  when  examined 

on  a  slide  under  the  microscope,  that  is 
peculiar  and  constant.  This  is  found  in  the  group 
micrococcus.  It  is  due  to  the  manner  of  multiplication ; 
the  bacilli  and  spirilli  multiply  by  division  through 


BACTERIOLOGY.  45 

their  shortest  diameter  only,  whereas  the  micrococci, 
having  one  diameter  the  same  as  another,  may  divide 
in  any  direction.  The  result  of  this  difference  in  the 
manner  of  dividing  is  that  the  relationship  of  individual 
bacteria  to  each  other  is  markedly  characteristic,  and 
permits  of  its  use  as  a  distinguishing  feature.  To 
distinguish  the  various  micrococci  from  each  other,  they 
are  therefore  divided  into  the: 

Staphylococci  (sing.,  staphylococcus) — when  they 
are  arranged  in  groups  which  bear  a  certain  resemblance 
to  a  bunch  of  grapes.  Diplococci  (sing.,  diplococcus) — 
when  they  are  arranged  in  pairs.  Streptococci  (sing., 
streptococcus) — when  they  are  arranged  in  chains, 
i.e.,  attached  end  to  end  in  lines  of  longer  or  shorter 
lengths. 

When  cocci  show  no  particular  arrangement  to  each 
other  they  are  simply  spoken  of  as  cocci  or  micrococci. 

The  foregoing  divisions  of  the  cocci  are  not  complete, 
since  there  are  other  peculiarities  of  grouping,  but 
those  enumerated  comprise  the  principal  pathogenic 
micrococci. 

Bacteria  may  be  said  to  be    universally 

DiSTRIRTT- 

distributed,  beinej  found  wherever  animals 

TION.  'to 

and  plants  are.  They  are  in  the  air  we 
breath,  and  in  the  water  we  drink.  The  surface  of 
the  earth  is  covered  with  them;  in  fact  the  ground  is 
their  natural  home,  which  should  not  surprise  us  since 
there  organic  matter  is  found  in  greatest  abundance. 


46         INFECTIOUS  AND  PARASITIC  DISEASES. 

Indeed,  the  source  of  the  bacteria  that  are  in  the  air 
and  water  is  the  ground.  They  are  carried  by  the 
winds  with  dust,  to  which  they  adhere,  and  by  water 
flowing  over  the  ground.  A  fact  of  great  importance 
to  be  remembered,  however,  is  that  bacteria  cannot 
rise  jrofn  liquids  that  contain  them  even  should  a  strong 
current  of  wind  blow  over  the  liquid. 

Upon  our  bodies  bacteria  are  constantly  present  in 
large  numbers,  and  in  every  cavity  leading  to  the  exterior, 
but  in  the  tissues  and  glands  of  the  healthy  person  they 
are  never  found.  The  number  of  bacteria  upon  the 
body  bears  a  relationship  to  the  cleanliness  of  the 
individual,  yet  even  in  the  most  cleanly  they  are  never 
absent. 

In  the  same  way  the  number  of  bacteria  in  any  locality 
is  likewise  related  to  the  number  of  persons,  to  the 
density  of  population,  and  to  the  efficiency  of  the 
measures  practised  in  the  disposal  of  waste.  Any 
kind  of  organic  matter,  whether  it  be  manure  heaps, 
the  waste  from  kitchens,  or  the  dejecta  and  secretions 
of  man  and  animals,  furnishes  appropriate  food  for 
these  scavengers.  The  chief  interest  for  us  in  this 
wide  distribution  of  bacteria  is  the  relationship  of  their 
presence  to  man  and  animals,  especially  in  that  it 
draws  attention  to  the  danger  of  contamination  of  the 
ground,  the  water,  and  food-stuffs  from  persons  and 
animals  suffering  from  bacterial  diseases,  and  the 
spread  in  consequence  of  disease  in  this  way. 


BACTERIOLOGY.  47 

The  statement  made  a  few  lines  above 
Ground,     that   "the   natural   home   for   bacteria   is 

the  ground"  applies  to  bacteria  in  general, 
and  as  the  saprophytes  comprise  the  majority  of  bac- 
teria, it  is  to  them  chiefly  that  reference  is  made. 
Nevertheless,  almost  any  pathogenic  bacterium  may 
find  in  the  soil  a  favorable  environment  for  a  longer  or 
shorter  period ;  and  even  in  the  event  that  multiplication 
cannot  take  place,  the  conditions  may  be  such  as  to 
preserve  its  vitality  unimpaired.  Therefore,  as  a  result 
of  the  careless  disposal  of  infectious  material  and 
discharges,  the  soil  is  often  contaminated  by  micro- 
organisms of  a  dangerous  character.  All  pathogenic 
microbes  in  the  soil  are  potentially  dangerous,  yet  the 
possibilities  for  them  doing  harm  is  not  the  same  for 
each,  since  it  depends  upon  the  species  of  micro-organ- 
ism, the  physical  environments  of  the  soil,  and  the 
purposes  for  which  the  soil  is  used.  It  should  always 
be  remembered  that  when  a  soil  is  contaminated  with 
infectious  matter,  the  bacteria  present  in  it  will,  in  dry 
weather,  be  carried  into  the  air  with  dust,  and  in  that 
way  may  find  their  way  into  our  lungs  or  contaminate 
our  foods.  The  most  widely  distributed  bacterium 
in  the  air,  and  the  most  'generally  dangerous,  is  the 
tubercle  bacillus.  The  typhoid  bacillus  is  the  most 
frequent  pollutor  of  wells  and  streams,  although  it 
may  become  a  most  dangerous  infection  in  the  air  if 
the   contamination   of  the   soil   is   excessive   and   the 


48         INFECTIOUS  AND  PARASITIC  DISEASES. 

hygienic  conditions  under  which  exposed  individuals 
live  are  especially  bad.  Just  such  a  condition  as  de- 
scribed pertained  in  the  great  military  camps  during  the 
Spanish-American  war,  and  the  commission,  appointed 
by  the  Surgeon- General  of  the  army  to  report  on  the 
prevalence  of  typhoid  fever  among  these  troops, 
ascribed  the  stupendous  morbidity  to  a  few  factors 
chiefly,  not  the  least  important  of  which  was  the  pres- 
ence of  typhoid  bacilli  in  the  dust  surrounding  the 
camps. 

Another  way  in  which  germs  in  the  soil  may  infect 
persons,  and  this  is  true  particularly  of  the  typhoid 
bacillus  and  the  cholera  spirillum,  is  for  the  microbes 
to  become  attached  to  vegetables  grown  in  the  soil, 
especially  if  these  vegetables  are  such  as  are  usually 
consumed  raw.  However,  whilst  the  majority  of 
pathogenic  bacteria  in  the  soil  may  be  regarded  as 
accidental  contaminations,  there  are  a  few  whose 
natural  habitat  is  the  ground.  These  are  the  tetanus 
bacillus,  the  bacillus  of  gaseous  edema,  and  the  bacillus 
of  malignant  edema.  In  countries  where  bubonic 
plague  is  epidemic,  the  specific  bacillus  (bacillus 
pestis)  seems  to  find  a  favorable  environment  in  the 
ground. 

As  has  been  said,  water  is  most  frequently 

Water,      polluted  by  the  washings  from  contami- 
nated soil.     The  pathogenic  bacteria  most 
feared  in  water  or  ice  are  the  cholera  spirillum  and  the 


BACTERIOLOGY.  49 

typhoid  bacillus,  on  account  of  the  danger  of  taking 
them  into  our  intestinal  tracts.  Because  cholera  and 
typhoid  fever  are  most  frequently  contracted  from  the 
drinking  of  polluted  water,  they  are  both  spoken  of  as 
^^ water-home  diseases. ^^  The  same  micro-organisms 
are  also  common  contaminators  of  other  foods,  the 
source  of  the  contamination,  as  a  rule,  being  also 
water,  whether  it  be  used  to  cleanse  utensils,  or  a  con- 
taminated stream  in  which  water-cress  or  oysters  are 
growing. 

The  danger  of  air  as  a  medium  for  the 
Air.        distribution    of    pathogenic    bacteria   has 

been  much  exaggerated,  in  fact,  even  the 
number  of  all  kinds  of  bacteria  in  the  atmosphere  is 
not  as  great  as  is  popularly  supposed.  True!  they  are 
practically  present  everywhere,  except  at  sea  many 
miles  from  shore,  and  at  great  altitudes;  yet  they  are 
never  present  in  such  abundance  that  ''it  rains  bacteria." 
At  one  time  the  profession  believed  that  the  infectious 
agents  of  many  diseases  were  carried  in  the  air  even 
considerable  distances,  a  belief  no  longer  held  since  the 
importance  of  the  role  that  insects  play  in  the  trans- 
mission of  disease  has  been  recognized. 

The  most  widely  distributed  pathogenic  micro- 
organism in  the  air  is  the  tubercle  bacillus,  the  cause  of 
consumption,  and  a  large  variety  of  other  ailments, 
such  as  hip- joint  disease,  caries  of  the  spine,  etc. 
Over  100,000  persons  die  annually  from  consumption 


50         INFECTIOUS  AND  PARASITIC  DISEASES. 

alone  in  United  States,  and  it  is  estimated  that  there 
are  over  2,000,000  of  people  afflicted  with  this  disease 
in  one  form  or  another.  All  of  these  sufferers  are 
expectorating  billions  of  tubercle  bacilli  daily.  Many 
of  them  are  engaged  in  earning  a  livelihood,  which  takes 
them  into  offices  and  homes,  the  atmosphere  of  which 
they  contaminate  by  coughing,  sneezing,  and  expec- 
torating. The  atmosphere  of  our  cities  is  vitiated  in 
the  same  way,  but  with  less  danger  to  others ;  for  in  the 
open,  through  the  action  of  sun-light,  through  heat, 
dilution,  and  other  physical  agencies,  the  virulence 
of  the  bacilli  is  gradually  diminished,  and  eventually 
destroyed;  finally  the  bacteria  themselves  are  disinte- 
grated. But  in  confined  spaces,  little  or  no  destruction 
of  the  bacilli  takes  place,  so  that  there  ensues  in  a  short 
time  an  atmosphere  ladened  with  tubercle  bacilli, 
which  is  highly  dangerous  to  everyone  who  breathes 
it.  The  dangerous  condition  of  such  an  atmosphere 
is  attested  by  the  frequency  of  tuberculosis  among 
successive  tenants  of  a  house  that  was  the  abode,  for  a 
period,  of  a  consumptive.  In  quiet  breathing,  no 
tubercle  bacilli  are  projected  into  the  air,  but  in  sneezing 
and  coughing  they  are;  and  in  the  expectoration,  esti- 
mates of  their  numbers  cannot  be  placed  too  high. 
Thus  it  is  that  the  tubercle  bacilli  find  their  way  to 
the  ground,  become  dry,  are  ground  up  with  the  dust, 
and  with  the  latter  are  carried  into  the  air  and  inhaled. 
The  moral  is  obvious. 


BACTERIOLOGY. 


SI 


Pathogenic  bacteria  are  either  specific 
or  non-specific  according  as  they  produce 
a  specific  or  non-specific  disease.  In  each 
of  these  classes  are  found  cocci,  bacilh,  and 
spirilla.  The  following  table  contains  the 
most  important  specific  and  non-specific  bacteria: 


SPEcrFic 
AND  Non- 
specific 
Bacteria. 


Non-specific  Bacteria. 

Micrococci 
Staphylococcus  pyogenes 

aureus 
Staphylococcus  pyogenes 

citreus 
Staphylococcus  pyogenes 

albus 
Streptococcus     pyogenes 

(Strep,  erysipelatis) 
Pneumococcus 
Tetragenus  albus 
Tetragenus  citreus 

Bacilli 
Colon  group 
Pneumo-bacillus  group 
B.  Pyocyaneus 
B.  Malignant  edema 
B.  Aerogenes  capsulatus 
B.  Proteus  vulgaris 

Specific  Spirilla 
S.  Recurrent  fever 
S.  Asiatic  cholera 
\  Spirochaeta  pallida  (syphilis) 


Specific  Bacteria. 
Micrococci 
Gonococcus 
Diplococcus  intracellularis 

meningitidis 
Micrococcus    melitensis 

(Malta  fever) 
Bacilli 
B.  Anthrax 
B.  Diphtheria 
B.  Glanders 
B.  Typhoid 
B.  Influenza 
B.  Tuberculosis 
B.  Leprosy 

B.  Pestis  (bubonic  plague) 
B.  Tetanus  (lock-jaw) 
B.  Dysentery 


52         INFECTIOUS  AND  PARASITIC  DISEASES. 

To  separate  one  species  of  bacteria  from 
Spores.  another,  bacteriologists  find  it  necessary 
to  note  with  the  greatest  accuracy  the 
minutest  differences  in  size,  shape,  arrangement, 
motihty  or  non-motihty,  etc.,  of  the  individuals  of  each 
species;  also  the  appearances  of  the  species  when 
viewed  as  masses  with  the  naked  eye.  To  do  this  the 
bacteria  are  grown  upon  various  artificially  prepared 
foods,  called  "culture  media,"  which  are  valuable  in 
bringing  out  the  peculiarities  of  the  different  species. 
By  means  of  cultures,  the  various  species  are  also 
separated  one  from  the  other,  and  the  individual 
characteristics  studied.  But  these  distinguishing  char- 
acteristics can  have  little  interest  for  anyone  unless 
he  works  with  bacteria  in  the  laboratory.  However, 
one  biological  characteristic  is  of  very  great  importance 
to  the  practical  sanitarian.  Reference  is  made  to  a 
resting  form  of  certain  of  the  bacteria  that  is  known  as 
a  spore.  A  spore  is  a  glistening  oval  body  into  which  a 
bacterium  is  converted  when  the  environment  is  un- 
favorable to  its  growth.  It  corresponds  to  the  seeds 
of  a  plant.  The  spore-form  of  bacteria  represents 
more  than  a  resting  stage,  however,  since  by  virtue  of 
an  investing  membrane,  they  are  far  more  resistant  to 
every  destructive  agency  than  the  yegetative  form. 
Thus  while  a  temperature  of  60°  Centigrade  (140°  F.) 
kills  the  vegetative  form  of  almost  every  bacterium  in  a 
few  minutes,  spores  are  able  to  withstand  the  boiling 


BACTERIOLOGY.  53 

point  for  an  hour  or  longer.  Likewise,  while  a  three 
to  five  per  cent  solution  of  carbolic  acid  kills  most  bac- 
teria in  half  an  hour,  there  are  spores  that  can  live  for 
days  in  the  same  strength  of  this  acid. 

Obviously,  therefore,  the  sporulating  bacteria  are  of 
very  great  importance.  Happily  the  number  of  sporu- 
lating bacteria  is  small,  a  fact  which  lessens  the  difii- 
culty  in  disinfection,  once  these  species  are  known. 
The  principal  sporogenous  (spore-producing)  bac- 
teria are  the  tetanus  bacillus,  the  anthrax  bacillus,  the 
bacillus  of  malignant  edema,  the  bacillus  aerogenes 
capsulatus,  and  probably,  the  actinomyces  bovis  and 
Madurae.  Fortunately,  not  one  of  these  bacteria  is  the 
agent  of  a  pestilential,  epidemic  disease. 

FACTORS  NECESSARY  TO  THE  GROWTH  OF  BACTERIA. 

The  factors  necessary  to  the  growth  of  pathogenic 
bacteria  are  deserving  of  as  much  attention  as  the 
means  devised  for  destroying  them;  indeed,  all  methods 
which  aim  at  destroying  them  (disinfection)  must 
needs  be  faulty  unless  attention  is  paid  to  the  conditions 
under  which  they  flourish.  The  means  are  not  always 
at  hand  to  employ  those  chemical  and  physical  agents 
that  experience  has  taught  may  entirely  be  relied  upon. 
Nor  if  they  are,  do  the  exigencies  of  the  case,  on  account 
of  the  destructive  action  on  fabrics  of  the  most  eflicient 
disinfectants,  or  the  bulk  of  the  material  to  be  disin- 
fected, permit  of  their  use.     Furthermore,  dissemina- 


54         INFECTIOUS  AND  PARASITIC  DISEASES. 

tion  of  the  infectious  agents  may  be  so  wide-spread  as  to 
make  actual  contact  between  the  usual  disinfectants 
and  the  infectious  agents  (an  essential  condition  for 
satisfactory  disinfection)  absolutely  impossible.  Un- 
der the  several  circumstances  enumerated,  it  is  self- 
evident  how  valuable  is  the  knowledge  of  the  conditions 
most  favorable  to  the  growth  of  bacteria,  since  by 
removing  favoring  conditions  and  substituting  harmful 
ones,  we  can  make  use  of  most  excellent  means  for 
exterminating  them.  In  the  discussion  which  follows, 
only  the  conditions  favorable  to  the  growth  of  patho- 
genic bacteria  are  treated. 

There  are  five  factors  principally  concerned  in  the 
growth  of  bacteria,  any  alterations  of  which  may  be 
regarded  as  distinctly  unfavorable;  these  relate  to  food, 
moisture,  temperature,  light,  and  relation  to  oxygen. 

Pathogenic  bacteria  require  organic  (albu- 
FooD.        minous)    material    upon   which   to    feed. 

It  makes  little  difference  what  the  source, 
whether  vegetable  or  animal,  solid  or  fluid,  fresh  or 
putrid,  they  are  adapted  to  all  kinds.  The  blood  and 
tissues-juices  of  the  animal  body  form  an  especially 
good  medium.  Besides  being  albuminous,  the  material 
must  have  an  alkaline  reaction.  Nearly  all  bacteria 
grow  best  in  a  slightly  alkaline  medium,  and  high 
alkalinity,  or  moderate  acidity,  either  stays  their  growth 
or  destroys  them.  Hence  the  strong  acids  and  alkalies 
are  true  disinfectants. 


BACTERIOLOGY.  55 

Moisture   is   essential   to   the   growth   of 
Moisture,     bacteria,  in  fact,  complete  drying,  except 

in  the  case  of  spores,  is  followed  by  death. 
Thus  the  spirilla  of  Asiatic  cholera  are  killed  in  a  few 
minutes  by  drying.  However,  too  much  reliance  can- 
not be  placed  on  this  factor,  since  an  infinitesimal 
amount  of  moisture  suffices  to  keep  them  alive  indefi- 
nitely. 

The  most  favorable  temperature  for  the 
Tempera-  gj-Q^^-]^  ^f  pathogenic  bacteria  is  that  of 
''''^^'  our  bodies,  98.6°  F.  (37°  C).  They  will 
also  readily  multiply  at  lower  temperatures  if  other 
circumstances  permit.  Thus  the  temperature  of  the 
ordinary  summer  day  (70°  F.,  24°  C.)  is  sufficient  for 
rather  rapid  multiplication.  Below  this  temperature, 
however,  growth  becomes  slower  as  the  temperature  is 
reduced,  and  practically  ceases  at  16°  C.  (60.8°  F.). 
Above  the  temperature  at  which  bacteria  grow  best 
(optimum  temperature),  only  a  few  degrees  suffice  to 
prevent  growth  (43°  C,  109.4°  F.). 

Oxygen  is  another  essential  to  the  growth 
Oxygen,      of    bacteria,    but    there    is    considerable 

difference  in  the  manner  in  which  the 
various  species  obtain  it.  The  majority  grow  best  when 
oxygen,  as  found  in  the  air,  is  supplied.  A  majority, 
however,  will  not  grow  in  the  presence  of  free  oxygen, 
being  compelled  to  obtain  their  oxygen  from  material 
in  which  it  is  in  combination  with  other  elements. 


56         INFECTIOUS  AND  PARASITIC  DISEASES. 

According  as  bacteria  grow  in  the  presence  or  absence 
of  oxygen  they  are  called  aerobes  or  anaerobes  resiptctiYely. 
Most  of  the  aerobic  bacteria  grow  as  well  without  free 
oxygen  as  with  it,  for  which  reason  they  are  spoken  of  as 
facultative  anaerobes;  but  the  contrary  is  not  true;  there 
are  few  facultative  aerobes. 

All   bacteria   grow   best   when   protected 

Light.       from   light.     This   statement   holds  good 
whether  the  light  be  natural  or  artificial. 

These  five  factors  are  the  chief  ones  favorable  to  the 
growth  of  bacteria,  and  to  the  retention  of  their  native 
characteristics  and  qualities.  Variations  in  favoring 
factors,  if  not  sufficient  to  destroy  them,  always  tend  to 
modify  their  functions  (prevent  growth,  etc.),  alter  their 
qualities  (diminish  virulence),  and,  to  a  certain  extent, 
produce  variations  in  form.  Broadly  speaking,  varia- 
tions acting  in  this  way  are  antiseptics  as  opposed  to 
disinfectants,  which  latter  are  the  means  used  to  destroy 
bacteria.  Modifications  in  favoring  factors  are  all 
the  time  in  nature  acting  to  reduce  the  rapidity  of 
multiplication  of  bacteria,  or  to  prevent  it  entirely; 
or  by  destroying  their  virulence  to  curtail  their  power 
to  do  harm.  Most  excellent  use  has  been  made  of  our 
knowledge  of  the  growth  of  bacteria  both  in  clinical 
and  preventive  medicine.  In  the  treatment  of  wounds 
suspected  of  containing  the  tetanus  bacillus,  it  is  the 
practice  to  leave  the  wound  exposed  to  the  air,  because 
we  know  that  the  tetanus  bacillus  will  not  grow  in  the 


BACTERIOLOGY.  57 

presence  of  atmospheric  air ;  some  physicians  go  a  step 
farther  and  advise  the  spraying  of  such  wounds  with 
oxygen.  In  the  preparation  of  some  of  the  vaccines, 
bacteria  whose  virulence  has  been  reduced  or  destroyed 
through  subjecting  them  to  unfavorable  surroundings 
are  used  for  the  inoculations,  a  form  of  vaccination 
that  is  now  being  practised  in  typhoid  fever  and  bubonic 
plague.  Because  cold  retards  bacterial  growth,  is  one 
good  reason  for  its  use  in  inflammations.  When  the 
urine  is  alkaline,  as  is  usually  the  case  in  inflammations 
of  the  bladder  (cystitis),  every  effort  is  made  to  change 
the  reaction  to  acid  and  thereby  make  the  urine  an  un- 
favorable medium  for  the  bacteria  which  cause  the 
cystitis. 

AGENTS  HARMFUL  TO  BACTERIA. 

Agents  which  prevent  the  growth  and  activity  of 
bacteria  without  destroying  them  are  called  antiseptics; 
those  that  destroy  them,  disinfectants  or  germicides. 
Disinfection  has  as  its  object  only  the  destruction  of 
pathogenic  microbes.  When  an  object  has  been  ren- 
dered free  from  all  kinds  of  micro-organisms  and  their 
spores  it  is  said  to  be  sterile,  and  the  process  by  which 
sterility  is  brought  about  is  known  as  sterilization. 

A  deodorant  is  a  substance  that  has  the 

Deodorant,    power  to  destroy  a  noxious  odor,  usually 

by  substituting  its  own  in  place  of  the 

other.    A  deodorant  may  or  may  not  be  a  disinfectant. 


58         INFECTIOUS  AND  PARASITIC  DISEASES. 

Most  of  the  disinfectants  are  also  deodorants,  but  the 
reverse,  it  is  to  be  remembered,  is  not  true.  Thus  for- 
mahn  and  carboHc  acid  are  both  deodorant  and  disin- 
fecting substances,  whereas  musk,  a  deodorant,  has  no 
disinfecting  power.  Bichloride  of  mercury,  a  most 
powerful  disinfectant,  is  only  a  deodorant  if  it  is  allowed 
to  act  for  a  long  period,  for  which  reason  it  cannot  be 
used  for  this  purpose  in  the  sick-room.  All  of  the  dis- 
infectants, when  diluted,  are  also  antiseptics.  This 
is  important,  in  as  much  as  in  the  strengths  that  many 
of  them  are  disinfectants,  they  are  injurious  to  the 
tissues  of  the  body.  Bichloride  of  mercury  1-50,000 
is  an  efficient  antiseptic,  yet  a  strength  of  i-iooo  is 
required  to  kill  all  bacteria  and  their  spores.  The 
same  is  true  of  formalin,  which  is  antiseptic  in  a  solution 
of  1-50,000,  germicidal  only  in  a  strength  of  3  to  5 
per  cent.  Substances  like  boracic  acid,  iodoform,  etc., 
on  the  other  hand,  are  purely  antiseptic,  even  when 
employed  in  concentrated  form.  Strong  solutions  of 
sugar  and  salt,  as  used  for  domestic  purposes  to  pre- 
serve various  edibles  from  spoiling,  are  antiseptic  but 
not  germicidal. 

The  prominent  place  occupied  by  insects 

InSECTI-  .  r     1'  1  •  .         . 

as  carriers  of  disease  has  given  rise  to  a 

CIDES.  .  .  ^  .  , 

new  interest  in  substances  that  will  kill 
them.  Interest  centers  chiefly  in  the  discovery  of  an 
efficient  substance  that  will  be  non-poisonous,  yet 
generally  applicable.     A  substance  combining  both  of 


BACTERIOLOGY.  59 

these  qualities  has  not  yet  been  discovered.  Substances 
used  to  kill  insects  are  called  insecticides.  Nearly  all 
the  disinfectants  are  insecticides;  formalin  is  a  notable 
exception.  The  most  important  insecticides  are  given 
in  a  later  chapter. 

Towards  agents  which  have  a  harmful  action  upon 
them,  i.e.,  either  interfere  with  their  growth  (antisep- 
tics), or  destroy  them  (disinfectants  or  germicides), 
bacteria  exhibit  distinct  differences  in  resistance — a 
characteristic  which  varies  with  the  species.  Species 
which  produce  spores,  are  not  more  resistant  to  injurious 
agencies  when  in  the  vegetative  state,  than  are  the 
ordinary  non-sporulating  bacteria.  But  in  the  form 
of  spores  their  power  to  resist  destruction  is  often 
marvelous.  However,  it  is  not  only  the  sporogenous 
form  which  is  difficult  to  deal  with;  there  are  a  few 
species  which,  although  they  do  not  produce  spores, 
are  nevertheless  almost  as  difi&cult  to  kill.  The  tubercle 
bacillus  is  one  of  these,  and  it  is  due  to  this  fact,  in  con- 
junction with  the  universal  prevalence  of  tuberculosis, 
that  the  tubercle  bacillus  has  a  wider  distribution  in 
nature  than  any  other  specific  pathogenic  micro-or- 
ganism. 

The  most  wide-spread  destruction  of  bacteria  is 
brought  about  through  natural  forces.  Where  actual 
destruction  is  not  accomplished,  the  same  influences  so 
modify  their  characteristics  as  to  render  them  inert. 
It  is  in  this  way  that  pathogenic  bacteria  are  robbed  of 


6o         INFECTIOUS  AND  PARASITIC  DISEASES. 

their  virulence  and  made  harmless.  Undoubtedly 
the  limitation  of  infectious  diseases,  which  otherwise 
would  be  impossible  of  control,  is  brought  about  in  this 
manner.  Nature's  means  are  simple,  yet  all-pervading, 
wherefore  she  accomplishes  more  than  the  combined 
efforts  of  men.  And  her  forces  are  effective,  and  always 
at  our  disposal,  so  that  it  behooves  us  to  learn  her  ways 
and  profitably  make  use  of  her  bounty.  The  forces 
which  nature  employs  are  chiefly  light,  drying,  dilution, 
cold,  and  symbiosis  (association). 

Among  the  natural  agencies  destructive  to 
Light.  bacteria,  sun-light  occupies  the  first  place. 
It  is  by  far  the  greatest  destroyer  of  germ- 
life.  Few  microbes  can  live  in  direct  sun-light  many 
hours,  the  pathogenies  being  especially  susceptible  to  its 
influence.  Its  destructive  influence  is  exerted  whether 
the  bacteria  are  in  a  dry  state,  or  in  a  liquid.  Moreover, 
it  acts  upon  them  whether  the  solution  is  clear,  or  is  as 
foul  as  sewage.  For  example,  only  twelve  hours' 
exposure  to  direct  sun-light  is  required  to  render  sewage 
free  from  bacteria,  i.e.,  sterile.  It  also  kills  spores,  if 
the  exposure  is  longer. 

Sun-light  has  the  power  of  acting  directly 

Dryness,     upon  bacteria  in  liquids,  as  has  just  been 

stated.     But  it  has  another  action  equally 

important  which  enhances  its  disinfecting  powers  to  a 

point  scarcely  equaled   by  any  gaseous  disinfectant, 

namely,  drying.    With  the  exception  of  spores,  com- 


BACTERIOLOGY.  6i 

plete  drying  practically  kills  all  pathogenic  bacteria. 
This  statement,  however,  is  only  true  where  complete 
drying  is  accomplished,  a  matter  that  we  can  never  be 
sure  of  unless  we  control  the  situation  as  is  done  in  the 
laboratory. 

Besides  sun-light  and  drying,  ozone 
Ozone.       (nascent   oxygen)  also   takes  part  in  the 

destruction  of  bacterial  life.  But  as  this 
substance  as  formed  in  nature  occurs  only  in  small 
quantities,  its  importance  in  this  respect  is  difficult  to 
measure.  More  ozone  is  found  in  the  country  than  in 
cities,  a  factor  that  undoubtedly  contributes  to  the 
greater  healthfulness  of  rural  surroundings. 

Cold,  we  have  already  learned,  is  unfavor- 
CoLD.        able  to  the  growth  of  bacteria.    At  the 

freezing  temperature  (32°  F.,  0°  C.)  most 
bacteria  succumb.  However,  some  species  exhibit  con- 
siderable resistance  to  freezing.  This  is  true  of  the 
micro-organisms  of  typhoid  fever  (typhoid  bacillus) 
and  Asiatic  cholera  (spirillum  of  Asiatic  cholera), 
epidemics  of  both  of  which  diseases  have  been  traced 
to  ice  as  the  source  of  the  infection. 

Dilution,  or  the  diminution  by  dilution,  of 

Dilution,    the   number   of   bacteria   per   volume   of 

material  in  which  they  are  contained,  is 

also  accomplished  by  nature.     How  great  a  benefit 

this  is  to  man  will  be  better  explained  in  a  succeeding 


62         INFECTIOUS  AND  PARASITIC  DISEASES. 

chapter.  Here  reference  is  only  made  to  the  fact  that, 
as  the  number  of  bacteria  which  get  into  the  body  plays 
a  highly  important  part  in  the  production  of  disease, 
adequate  dilution  of  infectious  agents  may  make  them 
innocuous.  Hence  one  value  of  dilution  is  evident. 
Another  effect  of  dilution  is  to  separate  the  individual 
microbes,  and  thereby  permit  of  closer  and  more 
thorough  contact  with  them  of  the  natural  destructive 
agencies.  In  practical  disinfection  dilution  of  the 
infectious  material  is  for  this  reason  always  practised. 
If  the  material  is  semi-solid  it  is  diluted  with  a  disin- 
fectant in  which  it  is  soluble;  or  it  is  broken  up,  if  not 
soluble,  to  permit  of  closer  contact  of  the  disinfectant 
with  as  much  of  the  material  as  is  possible.  If  liquids 
are  to  be  disinfected,  either  a  liquid  disinfectant  is  used, 
or  one  that  is  soluble  in  the  solution  to  be  disinfected. 
In  any  case,  sufficient  time  (one  hour  for  the  disinfec- 
tants in  common  use)  is  given  for  penetration. 

By    symbiosis    is    understood    the    living 

(  .  ^-  X  together  of  different  species  of  organisms 
(association).    .   ^  .  ^  ^ 

in  the  same  medium. 
It  further  implies  that  they  are  mutually  helpful  and 
beneficial.  Among  bacteria  in  nature  a  struggle  for 
existence  is  constantly  taking  place,  which  in  conjunc- 
tion with  other  natural  forces  serves  to  keep  their  num- 
bers within  limits.  Of  the  two  classes  of  bacteria, 
parasites  and  saprophytes,  the  saprophytes  are  the  more 
numerous  and  by  far  the  hardier,  so  that  when  they  are 


BACTERIOLOGY.  63 

growing  side  by  side  with  pathogenies,  the  latter  get 
less  food  and  suffer  from  the  excretory  products  of  the 
former.  Hence  in  the  process  of  putrefaction,  as  of 
sewage  or  of  diseased  carcasses,  self- purification  is 
largely  brought  about  by  the  saprophytes  crowding  out 
the  weaker  pathogenies. 

Another  natural  force  tending  to  the 
Bactericidal  destruction  of  bacterial  life  is  the  hacteri- 
PowER  OF  cidal^  action  of  the  body-juices  of  all 
Body-juices,  living   things.     The   number   of   bacteria 

which  rest  upon  our  bodies,  and  even  get 
into  the  interior,  is  incalculable,  yet  very  few  do  us 
harm  on  account  of  this  property  of  living  matter. 
This  protective  power  of  the  body  when  displayed 
against  a  disease  is  called  immunity. 

The  destructive  action  of  heat  upon  bac- 
Heat.        teria  is  so  well  known  that  it  often  comes  as 

a  surprise  that,  in  disinfection,  more  con- 
fidence should  be  placed  in  chemicals.  As  a  matter  of 
fact,  there  is  no  more  efficient  disinfectant  than  heat 
if  properly  applied.  It  is  also  the  cheapest.  With  few 
exceptions,  bacteria  are  killed  in  a  few  minutes  at  a 
temperature  considerably  below  the  boiling  point  of 
water;  and  at  the  boiling  point  at  once.  Yet  it  is  a 
common  practice  for  both  physicians  and  nurses  to  put 
a  family  to  considerable  expense  for  chemical  disinfec- 
tants in  a  case  of  typhoid  fever,  for  example,  when  heat 
♦Bacteria  destroying. 


64         INFECTIOUS  AND  PARASITIC  DISEASES. 

applied  directly,  or  several  times  the  quantity  of  boiling 
water  added  to  the  material  to  be  disinfected  (stools, 
for  instance),  and  the  mixture  allowed  to  stand  an  hour, 
is  as  trustworthy  a  practice  as  the  use  of  any  disinfec- 
tant; and  far  more  so  than  many  chemicals  whose 
virtues  are  highly  extolled  in  newspapers  and  medical 
journals. 

We  have  seen  that  although  the  optimum  temperature 
for  the  growth  of  pathogenic  bacteria  is  that  of  the  body 
(98.6°  F.),  they  will  multiply  at  a  much  lower  tempera- 
ture. Above  the  temperature  of  the  body,  however, 
the  hmit  is  small,  since  growth  ceases  at  109.4°  F.  (43°  C). 
At  140°  F.  (60°  C.)  the  vegetative  forms  of  practically 
all  bacteria  are  destroyed  if  applied  for  ten  minutes, 
and  the  time  required  to  destroy  them  diminishes  as 
the  temperature  rises.  At  212°  F.  (100°  C.)  as  we  have 
stated,  they  are  killed  immediately.  The  tubercle 
bacillus,  although  only  occurring  in  a  vegetative  form 
(i.e.,  does  not  form  spores),  is  an  exception  in  that 
boiling  for  five  minutes  is  required  to  destroy  it. 

There  are  a  large  number  of  substances 
Chemicals,     which    have    a    detrimental    effect    upon 

bacteria,  some  merely  inhibiting  their 
growth  (antiseptics),  others  destroying  them  (disinfec- 
tants). Their  number  is  too  great  to  enumerate.  Those 
that  interest  us  because  they  are  useful  in  rendering 
infectious  matter  harmless  will  be  given  in  a  later 
chapter. 


BACTERIOLOGY.  65 

Cleanliness  is  an  efficient  weapon  to 
Cleanliness,  employ  against  bacteria.  Too  much  can- 
not be  said  in  its^  favor.  Through  it  we 
can  dispose  of  the  most  essential  factor  in  the  growth 
of  bacteria,  namely,  organic  matter.  Where  organic 
matter  does  not  exist,  bacteria  cannot  live  and  multiply. 
Material  of  any  kind,  containing  bacteria,  is  said 
to  be  septic;  when  free  from  bacteria,  aseptic.  In 
practical  work,  e.g.,  surgery,  objects  and  persons  are 
rendered  bacteria-free  either  through  the  use  of  antisep- 
tics and  disinfectants,  or  by  mechanical  cleansing  with 
soap  and  water.  The  two  methods  are  distinguished 
as  the  antiseptic,   and  aseptic  methods  respectively. 


CHAPTER  III. 

PHENOMENA  OF  INFECTION. 

There  are  two  view-points  from  which  the  production 
of  an  infectious  disease  must  always  be  studied,  viz., 
(i)  the  infecting  micro-organism,  and  (2)  the  state  of 
the  body  at  the  time  the  infection  occurs.  Apart  from 
injuries  and  direct  poisonings,  there  are  no  independent 
causes  of  disease.  When  we  say  an  infectious  disease 
is  due  to  this  or  that  micro-organism,  we  are  making 
a  statement  which  expresses  only  a  fraction  of  the  true 
sequence  of  events,  since  unassisted,  infectious  agents 
probably  never,  under  the  ordinary  conditions  of  life, 
bring  about  disease.  To  be  sure,  their  presence  in  an 
infectious  process  is  indispensable,  yet  the  mere  fact 
of  their  presence  counts  for  naught  unless  the  body 
has  been  prepared,  so  to  speak,  for  their  invasion. 
Furthermore,  even  in  the  event  that  the  body  be  in  a 
most  favorable  condition  for  infection,  there  are  several 
conditions  which  micro-organisms  must  fulfill  before 
they  can  exercise  their  specific  functions.  For  the 
foregoing  reasons,  therefore,  an  infectious  disease  is  the 
result  of  the  co-existence  of  a  chain  of  fortuitous  phenom- 

66 


PHENOMENA  OF  INFECTION.  67 

ena  which  concern  the  body  on  the  one  hand,  and  the 
infectious  agents  on  the  other.     To  illustrate:  We  say 
that  the  pneumococcus    is  the   cause   of   pneumonia 
because  this  particular  micro-organism  is  found  in  the 
characteristic   expectoration   during   life,    and   in   the 
lungs  after  death.     Unquestionably,  it  is  a  necessary 
factor  in  the  disease ;  but  is  it  the  sole  factor  ?    We  have 
only  to  examine  the  facts  in  the  case  to  discover  that 
it  is  not.     In  the  first  place,  practically  everyone,  even 
in  health,  harbors  the  pneumococcus  in  his  mouth. 
In  the  second  place,  pneumonia  in  robust  individuals 
invariably  follows  either  fatigue  and  exposure  to  in- 
clement weather,  or  exposure  and  over-indulgence  in 
intoxicants;  often  a  combination  of  all  three  factors 
precedes  the   onset.     In  the  less  robust,   e.g.,   those 
suffering  from  chronic  ailments— (a  condition  in  which 
susceptibility  to  pneumonia  is  especially  marked)  it  is 
the  pre-existing  sub-normal  state  of  the  health  which 
permits  the  micro-organisms  to  invade  the  deeper  air- 
passages  and  produce  the  disease.     Again:  It  is  a  mat- 
ter of  common  observation  that  of  a  number  of  indi- 
viduals exposed  to  the  same  infectious  disease  not  all 
are  attacked,  and  that  in  those  susceptible  the  disease 
presents  extraordinary  variations  as  regards  its  mild- 
ness or  severity.     If  the  microbe  were  the  sole  factor 
concerned,  all  exposed  individuals  would  be  attacked, 
and  all  attacked  would  suffer  to  the  same  degree;  a 
thing  which  everyone  knows  never  happens.     More- 


68         INFECTIOUS  AND  PARASITIC  DISEASES. 

over,  a  person  may  resist  the  action  of  a  pathogenic 
agent  at  one  time  and  fall  victim  to  it  at  another. 

INFECTIOUS  AGENTS  IN  DISEASE. 

From  the  view-point  of  infectious  agents  there  are 
five  conditions  to  be  fulfilled  before  they  can  provoke 
disease : 

(i)  They  must  be  present  in  sufficient  numbers. 

(2)  They  must  reach  (what  is  for  them)  their  portal 
of  entry. 

(3)  They  must  be  virulent. 

(4)  In  the  case  of  certain  pathogenic  agents,  disease 
can  result  only  when  the  agent  is  accompanied  by  one 
or  more  other  micro-organisms,  or  when  accompanied 
by  a  foreign  body. 

(5)  If  a  disease  is  communicated  exclusively  by 
an  insect,  obviously  the  presence  of  that  insect  is  an 
essential  condition. 

Contrary  to  a  wide-spread  belief,  there  is 
Number,     no  disease  which  a  single  infectious  agent, 

acting  alone,  can  produce;  that  is  to  say, 
one  micro-organism  of  a  certain  species,  however  viru- 
lent it  may  be,  is  incapable  of  provoking  disease. 
Experimentally  it  has  been  found  that  even  in  animals 
very  susceptible  to  them,  it  takes  large  numbers  of  a 
particular  micro-organism  to  bring  about  characteristic 
results.  In  diseases  occurring  among  persons  we  have 
no  way  of  determining  the  number  of  germs  that  pri- 


PHENOMENA  OF  INFECTION.  69 

marily  enter  the  body,  yet  a  wealth  of  facts  gleaned 
through  experiments  upon  animals  leads  us  to  conclude 
their  numbers  must  be  large.     Clinical  observations 
also  furnish  some  data  in  support  of  this  view.     In 
cases  where  long  and  tedious  operations  are  performed, 
a  wound  is  often  exposed  to  the  air  for  hours  without  ill 
effects    following.     Certainly    no    one    believes    that 
during  the  time  of  exposure  and  manipulation  bacteria 
do  not  soil  the  wound.     On  the  contrary,  we  know  they 
do;  but  the  reason  harm  only  occasionally  results  from 
those  that  enter  is  attributed  to  the  fact  that  either  they 
are  present  in  insufficient  numbers  and  are  of  low 
virulence,  or  the  vital  forces  of  the  patient  are  sufficient 
to  destroy  them.     Similar  observations  are  made  by 
physicians  in  the  repair  of  injuries  in  which  either 
aseptic  or  antiseptic  precautions  are  utterly  impossible. 
Thus  in  the  practice  of  mid-wifery,  for  example,  al- 
though such  unfortunate  surroundings  are  quite  com- 
mon, cases  of  puerperal  fever  (child-bed  fever)   are 
so  infrequent  as  to  excite  comment.     Indeed,  puerperal 
fever  occurs  occasionally  under  conditions  in  which 
the  surroundings  are  ideal,  probably  through  the  ful- 
fillment of  the  third  condition  above  given,  viz.,  extra- 
ordinary virulence  of  the  germs. 

A  singular  peculiarity  of  pathogenic  micro- 
PoRTAL  OF  organisms  is  that  in  order  to  provoke  dis- 
Entry.  ease,  they  must  find  lodgment  in  or  upon 

that  portion  of  the  body  which  offers  the 


70         INFECTIOUS  AND  PARASITIC  DISEASES. 

least  resistance  to  their  attack.  The  tissues  of  the  body 
vary  in  susceptibihty  to  microbic  invasion,  the  differ- 
ence having  a  relation  to  the  species  of  organism.  Thus 
there  are  certain  bacteria  which  can  exert  a  specific 
action  only  when  they  gain  entrance  into  the  intestinal 
tract ;  to  this  class  belong  the  typhoid  bacillus  and  the 
spirillum  of  Asiatic  cholera.  There  are  bacteria,  on  the 
other  hand,  such  as  the  tetanus  bacillus,  the  gas  bacillus, 
and  the  common  bacteria  of  suppurations,  which  may 
be  swallowed  with  impunity,  in  fact  often  are,  their 
characteristic  effects  being  produced  only  by  entrance 
into  a  wound  of  the  skin  or  a  mucous  membrane. 
Similarly,  the  diphtheria  bacillus  has  no  effect  upon  the 
unbroken  skin,  nor  upon  the  mucous  membranes  of  the 
stomach  or  intestines,  although,  in  the  disease,  countless 
numbers  are  swallowed;  it  selects  per  force  the  mucous 
membranes  of  the  nose,  the  pharynx,  and  the  posterior 
nares  chiefly,  less  often  those  of  the  conjunctiva  and 
the  vulva. 

The  channel  of  entry,  therefore,  occupies  an  impor- 
tant position  when  the  subject  of  a  micro-organism's 
pathogenicity  is  under  consideration,  since  upon  it  will 
depend  the  result  of  the  presence  of  a  pathogenic  agent 
whether  the  latter  does  or  does  not  satisfy  every  other 
condition  necessary  for  its  specific  action. 

The  real  power  of  every  species  of  micro- 
ViRULENCE.     organism  which  produces  disease  lies  in 

its  ability  to  secrete  one  or  more  toxins. 


PHENOMENA  OF  INFECTION.  71 

When  it  has  this  power  it  is  said  to  be  virulent.  In 
another  chapter  the  remarkable  inconstancy  of  the 
toxicity  of  micro-organisms  has  been  considered  (vide 
p.  41).  That  virulence  in  bacteria  is  an  essential 
phenomenon  in  disease-production  has  been  abundantly 
confirmed  by  the  finding,  in  their  propitious  channels 
of  entry,  of  various  pathogenic  micro-organisms  in 
perfectly  healthy  individuals,  the  organisms  so  found 
being  commonly  non-virulent  varieties. 

All  pathogenic  bacteria  vary  in  respect  to  virulence, 
and,  as  has  been  explained  in  a  previous  chapter,  are 
on  this  account  divided  into  those  which  are  virulent 
and  those  which  are  non- virulent.  However,  it  should 
be  remembered  that  non-virulent  bacteria  are  not 
without  danger  to  individuals  who  carry  them,  and  to 
other  persons  to  whom  they  may  be  conveyed,  since 
they  may  acquire  virulence  either  before  or  after  trans- 
ference, and  provoke  disease. 

Microbic  association  in  disease  is  of 
MicROBic  common  occurrence,  the  resulting  mixed 
Association  infection  usually  being  severer  than  an 
(symbiosis),     unmixed   one.     Thus   in   diphtheria,   the 

diphtheria  bacillus  is  often  associated 
with  the  streptococcus  pyogenes  or  the  staphylococcus 
pyogenes  aureus;  the  typhoid  bacillus  with  the  bacillus 
coli  communis^  a  common  inhabitant  of  the  intestinal 
tract.  There  are  some  bacteria,  however,  which  cannot 
exercise  their  power  without  the  co-operation  of  another 


72         INFECTIOUS  AND  PARASITIC  DISEASES. 

bacterium.  To  this  class  belongs  the  tetanus  bacillus, 
which,  being  an  obligate  anaerobic  bacillus  (cannot 
grow  in  the  presence  of  free  oxygen),  is  compelled  to 
work  with  another  germ  that,  by  absorbing  the  oxygen, 
makes  the  surroundings  favorable  for  its  growth. 
This  bacillus  also  works  mischief  chiefly  when  accom- 
panied by  a  foreign  body,  as  for  example  a  sliver,  powder- 
grain,  etc.,  or  where  there  has  been  much  laceration 
of  tissues.  The  same  thing  is  true  of  the  bacillus 
aerogenes  capsulatus. 

There  are  a  few  infectious  diseases,  such 
Conveyance  as  malarial  fever,  yellow  fever,  and  filaria- 
BY  Insects,     sis,    in   which   the   infectious   agents   are 

exclusively  conveyed  by  insects.  All  such 
diseases  are  due  to  animal  parasites,  which  for  com- 
plete development  require  two  hosts,  man  and  an  insect. 
Each  host  nourishes  the  parasite  during  one  phase  of 
its  growth  only,  so  that  in  order  to  reach  maturity  the 
latter  must  pass  consecutively  from  one  host  to  another. 
Furthermore,  since  parasites  are  restricted  to  especial 
hosts,  the  presence  of  an  appropriate  host  for  each  one 
is  imperative  if  they  are  to  be  perpetuated.  Therefore 
it  follows  that  the  communicability  of  a  disease  by  an 
insect  is  only  possible  in  the  event  of  the  presence  of 
that  particular  variety  of  insect.  So  circumscribed  is 
the  world  of  parasitism!  For  instance,  yellow  fever 
is  conveyed  by  only  one  genus  of  mosquito  (stegomyia 


PHENOMENA  OF  INFECTION.  73 

fasciata),  malarial  fever  by  a  few  varieties  of  another 
(anopheles),  etc. 

THE  BODY  IN  RELATION  TO  INFECTIONS. 

We  have  just  considered  the  exacting  conditions 
v^^hich  an  infectious  agent  must  fulfill  to  provoke  disease. 
The  fulfillment  of  these  conditions,  however,  only 
meets  the  requirements  in  so  far  as  the  micro-organism 
is  concerned,  and  therefore  presents  but  one  side  of  the 
problem;  the  other  side,  the  position  that  the  body 
occupies  in  relation  to  infections,  is  equally  important, 
and  it  is  to  this  phase  of  the  question  that  we  now  turn. 
A  few  lines  above,  this  statement  was  made,  "it  is  a 
matter  of  common  observation  that,  of  a  number  of 
individuals  exposed  to  the  same  infectious  disease,  not 
all  are  attacked;  and  in  those  susceptible,  the  disease 
presents  extraordinary  variations  as  regards  its  mildness 
or  severity.  If  the  microbe  were  the  sole  factor  con- 
cerned, all  exposed  persons  would  be  attacked,  and  all 
taking  the  disease  would  suffer  to  the  same  degree;  a 
thing  which  everyone  knows  never  happens.  Moreover, 
a  person  may  resist  the  action  of  a  pathogenic  agent  at 
one  time,  and  fall  victim  to  it  at  another."  The  ques- 
tion that  naturally  presents  itself  is,  what  brings  about 
such  radical  differences  in  the  vulnerability  of  individ- 
uals to  infectious  agents  ?  That  it  is  not  always  conse- 
quent upon  modifications  in  the  agents,  we  know  from 
observations    upon    patients,    and    experiments    upon 


74         INFECTIOUS  AND  PARASITIC  DISEASES. 

animals.  To  account  for  it,  there  is  obviously  some 
subtle  difference  in  the  vital  processes  of  different 
individuals,  and  in  the  same  person  at  different  times. 

Every  healthy  person  is  by  nature  endowed  with  the 
means  of  combating  disease,  but  his  natural  defenses, 
while  they  may  be  strengthened,  may  also  be  weakened 
by  those  forces  and  influences  which  surround  him. 
Nor  before  the  tribunal,  disease,  are  all  men  born  equal, 
since  progenitors  may  transmit  to  their  offspring  con- 
stitutions defective  in  defensive  force.  Furthermore, 
during  the  constructive  (infancy  and  childhood)  and 
degenerative  (old  age)  periods  of  life  the  protective 
forces  are,  on  the  other  hand,  weakened  through  imma- 
turity, on  the  other,  by  the  fact  that  they  are  declining 
with  age.  Therefore,  to  environment,  heredity,  and 
age,  must  we  look  for  an  explanation  of  any  imperfec- 
tion in  our  natural  resistance  to  disease. 

Predisposition.  The  absence  of  resistance  to 
disease,  i.e.,  susceptibility,  has  been  given  the  compre- 
hensive title  predisposition,  and  we  characterize  as 
predisposing  every  influence  or  cause  which  tends  to 
weaken  the  vital  forces  and  therefore  predisposes  to 
disease.  In  every  infection  such  causes  always  play 
an  important  role,  usually  more  important  than  the 
infectious  agents,  a  fact  to  which  too  little  heed  is  given 
in  the  hurly-burly  of  life.  The  attitude  of  the  world 
in  this  respect  is  not  unlike  its  greater  faith  in  the  cura- 
tive powers  of  drugs,  than  in  a  disciplinary  regulation 


PHENOMENA  OF  INFECTION. 


75 


of  its  habits.     If  we  should  symbohze  infectious  agents 
as  a  spider,  and  humanity  as  a  fly,  then  the  web  would 


f  Bacteria 


Infectious 

Agents 

DcicLeria 

Fungi 

Protozoa 

Race 

Family 

Individual 

^  Heredity  > 

Infectious 

Diseases 

-,     .        Climate 
Region  I 

Insects 
Season 
Occupation 
Poor  Food  or  Fasting 

Predisposing 
Causes  ' 

Environ- 
ment 

Unhygienic  Surroundings 
Previous  Disease 
Poisons  (Alcohol,  etc.) 

Injuries 

Loss  of 

Blood 

and        ^ 

Shock 
Laceration 

Operations 

of  Tissues 

Infancy 

Age           ^ 

Childhood 

Adolescence 

.  Old  Age 

76         INFECTIOUS  AND  PARASITIC  DISEASES. 

represent  predisposing  causes,  for  only  when  the  fly 
is  entangled  in  the  web  does  the  spider  attack  its  victim. 
It  will  be  observed  that  this  conception  of  disease 
does  not  undervalue  the  part  that  infectious  agents  play 
as  direct  or  exciting  causes  of  disease,  but  it  further 
recognizes  fully  the  preponderating  influence  of  those 
accessory,  auxiliary,  or  predisposing  causes  without 
which  the  animate  agents  cannot  act.  The  analytical 
chart  here  shown  aims  to  elucidate  graphically  this 
view.  To  be  sure,  all  of  the  diverse  elements  represented 
are  not  operative  at  the  same  time  in  any  infectious 
disease;  but  one  or  several  always  are,  and  these  act  in 
combination  with  the  infectious  agents. 

Referrinoj  to  the  chart,  it  will  be  seen  that 

there  are  three  sub-divisions  to  heredity, 
viz.,  race,  family,  and  individual. 

Our  knowledge  of  race  as  influencing 
Race.        infection  is  of  comparatively  recent  date. 

This  knowledge,  besides  having  an  impor- 
tant bearing  upon  etiology,  is  of  historical  interest  in 
explaining  the  errors  of  judgment  which  in  the  past  led 
to  great  crimes.  In  many  notable  epidemics  the  Jews 
were  singled  out  for  persecution,  because  they  escaped 
the  prevailing  scourge,  their  immunity  being  ascribed 
to  a  special  knowledge  of  the  epidemic  disease.  During 
cholera  epidemics,  the  relationship  to  drinking-water 
which  was  recognized,  they  were  accused  of  poisoning 
wells,  and  the  brutal  ferocity  of  insensate  mob- violence 


PHENOMENA  OF  INFECTION.  77 

was  visited  upon  them.  But  the  dispassionate  reason- 
ing of  scientific  investigation  has  acquitted  them  of 
those  charges  by  explaining  their  insusceptibihty  to 
infection  as  a  pecuharity  of  the  Hebrew  race.  Thus, 
by  far,  fewer  Jews  are  victims  of  pulmonary  tubercu- 
losis than  Gentiles,  and  Asiatic  cholera  is  so  rare  among 
them  as  to  lead  some  authors  to  doubt  that  it  ever 
occurs.  Furthermore,  they  suffer  less  severely  from 
other  infections,  and  less  from  animal  parasites,  than 
other  races.  However,  it  must  be  confessed  that  in  the 
case  of  the  Jews  (and  in  that  of  any  other  race,  for  that 
matter),  racial  characteristics  do  not  explain  entirely 
the  absence  of  predisposition.  We  should  err  greatly 
did  we  fail  to  take  into  account  a  race's  habits  and 
customs.  For  instance,  other  things  equal,  the  Jews 
are  better  housed,  'eat  more  wholesome  food,  are  more 
cleanly  in  their  habits;  take  better  care  of  their  children, 
and  are  less  given  *  to  intoxicants,  than  their  Gentile 
neighbors ;  while  all  of  them  are  still"  influenced  more  or 
less  by  thfe  Mosaic  laws.  Their  standard  of  life,  if 
adopted  by  any  people,"  would  tend  to  strengthen  its 
vital  resistance  and,  in  some  at  least,  would  lead  to 
the  establishment  of  the  antithesis  of  predisposition, 
namely,  immunity. 

Another  factor  which  exercises  its  influence  upon  a 
race's  susceptibility,  or  immunity,  is  the  length  of  time 
it  has  been  in  contact  with  a  disease.  The  first  con- 
flict of  a  race  with  an  infectious  disease  often  proves 


78         INFECTIOUS  AND  PARASITIC  DISEASES. 

highly  disastrous,  as  witness  the  terrible  ravages  of 
measles  among  the  natives  of  the  Faroe  Islands  in  1846, 
when  out  of  7,782  people,  6,000  were  attacked;  and  also 
the  invasion  of  the  Fiji  Islands  in  1875  by  the  same 
malady,  during  which  40,000  of  its  150,000  inhabitants 
died.  Nor  is  it  necessary  to  cite  examples  of  distant 
peoples;  in  our  own  country  we  have  an  object  lesson 
in  the  Negro  and  the  Indian.  The  Negro  is  three  times 
as  susceptible  to  tuberculosis  as  the  white  inhabitants; 
and  the  North  American  Indian  has  been  well-nigh 
exterminated  by  this  ''great  white  plague."  Generally 
speaking,  the  longer  the  contact  of  a  race  with  an 
infectious  disease,  the  less  is  its  predisposition  to  it. 
Tuberculosis  well  illustrates  this  point  in  the  respect 
that  the  most  ancient  race,  the  Jews,  suffers  least  from 
it;  other  races,  in  inverse  ratio  to  their  antiquity. 
Diminution  in  susceptibility  through  contact  is  prob- 
ably brought  about  by  large  numbers  of  individuals  in 
successive  generations  surviving  an  infection,  and 
transmitting  to  succeeding  generations  their  own  individ- 
ual resistance,  together  with  that  acquired  by  passing 
through  an  attack  of  the  disease.  Yet  after  every 
factor,  such  as  surroundings,  food,  contact  with  a 
disease,  etc.,  has  been  considered,  there  is  still  wanting 
an  explanation  of  the  fact  that  when  two  races  live 
side  by  side,  under  precisely  similar  circumstances, 
the  one  suffers  from  an  infectious  disease  to  a  greater 
extent  than  does  the  other.    Upon  no  other  grounds  than 


PHENOMENA  OF  INFECTION.  79 

racial  peculiarity,  can  this  be  explained.  Animals  also 
exhibit  the  same  peculiarity  in  susceptibility  to  disease. 
Among  cattle,  Jerseys  are  more  susceptible  to  tuber- 
culosis than  other  breeds.  Dogs  are  practically  immune 
to  it,  a  fact  which  probably  explains  the  high  position 
dog-fat  holds  among  the  ignorant  as  a  remedy  for  tuber- 
culosis. At  a  laboratory  at  which  the  writer  once 
worked,  and  where  many  dogs  were  used  for  experi- 
mental purposes,  the  janitor  sold  large  quantities  of 
the  fat  to  a  local  charlatan  who  in  turn  disposed  of  it  as 
a  specific  for  consumption.  It  must  not  be  supposed, 
however,  that  racial  immunity,  such  as  is  frequently 
the  case  with  individuals,  is  ever  perfect.  There  are 
always  families  and  individuals  whose  immunity  is 
diminished  by  marriage  and  environment,  and  the 
whole  race  is  subject  to  those  diseases  which  are  inci- 
dental to  age. 

As  the  family  partakes  of  the  characteris- 
Family.      tics  of  the  race,  family  predisposition  is 

subject  to  the  same  general  rules  as  de- 
scribed for  races,  with  the  exception,  that  marriage 
between  members  of  different  races  by  blending  the 
vital  forces  may  either  increase  or  decrease  the  power 
to  combat  disease.  A  similar  result  follows  the  union 
of  persons  of  the  same  family;  and  the  great  danger 
of  a  summation  of  highly  susceptible  strains  has  led, 
in  many  states,  to  the  wise  enactment  of  a  law  against 
consanguineous  marriages.     An  extension  of  this  law 


8o         INFECTIOUS  AND  PARASITIC  DISEASES. 

to  include  inebriates  and  consumptives  has  many 
arguments  in  its  favor. 

From  the  view-point  of  the  body,  individual 
Individual,     predisposition   is   the  principal   factor   in 

the  spread  of  infectious  diseases.  With 
few  exceptions  it  is  operative  in  every  case,  so  that  the 
study  of  the  various  conditions  which  lead  to  it  involves 
considerations  of  the  highest  importance  to  physicians, 
nurses,  and  sanitarians  generally.  Individual  predis- 
position may  either  be  inherited  or  acquired.  If  inher- 
ited, it  is  seldom  to  any  particular  infection  but  to  all. 
We  no  longer  believe  in  an  inherited  predisposition 
to  a  special  disease,  as  was  formerly  the  case  with  tuber- 
culosis, but  rather  in  the  inheritance  of  an  especially 
susceptible  state  of  the  body-tissues  which  predisposes 
to  all  manner  of  infections.  Not  alone  are  the  children 
of  the  consumptive  markedly  prone  to  consumption 
but  also  the  children  of  all  parents  who  at  the  time  of 
conception  were  either  in  an  impoverished  state  of 
health  from  disease,  or  whose  vital  resistance  was 
depressed  by  alcohol,  drugs,  or  by  deprivations  of  one 
kind  or  another.  The  reason  that  the  consumptive's 
offspring  has  fewer  chances  of  escaping  tuberculosis 
than  the  child  of  the  non-tuberculous,  is  because  the 
atmosphere  of  its  home  is,  in  the  majority  of  cases, 
through  ignorance,  vitiated  by  the  germs  of  its  parent's 
malady.  Besides  a  general  predisposition  such  as  we 
have  been  discussing,  a  predisposition  to  local  disorders 


PHENOMENA  OF  INFECTION.  8i 

is  also  recognized.  This  relates  to  a  susceptibility  of 
certain  organs  or  tissues  as  a  result  of  other  concurrent 
infections.  Thus,  rheumatism  predisposes  to  infections 
of  the  heart;  diabetes,  to  suppurative  inflammations 
(carbuncles)  and  gangrene  of  the  skin  and  subcutaneous 
tissues;  enlarged  tonsils  and  adenoids  to  colds,  tonsil- 
litis, and  probably  diphtheria. 

Under  environment  is  included  all  those 
external  influences  by  which  man  is  sur- 

MENT.  .  ^ 

rounded  which,  by  exercising  a  deleterious 
influence  upon  health,  predispose  him  to  disease. 
Among  such  influences  are  region,  season,  occupation, 
food,  unhygienic  surroundings,  previous  disease,  poisons, 
injuries,  etc. 

Locality  may  act  as  a  predisposing  cause 
Region,     in  many  ways,  all  of  which  may  be  grouped 

under  two  heads,  viz.,  (i)  climate,  and  (2) 
physical  conditions. 

Climatic  conditions,  as  is  well  known, 
Climate,     differ  widely  in  various  parts  of  the  world, 

from  which  arise  for  the  most  part  great 
differences  in  plant  and  animal  life.  Moreover,  practi- 
cally everywhere,  there  are  seasonal  variations  more  or 
less  pronounced,  which  have  their  corresponding  in- 
fluence upon  all  living  things.  In  tropical  and  sub- 
tropical countries  where  a  high  mean  temperature  and 
a  maximum  amount  of  moisture  predominate,  the 
luxuriance  of  the  foliage  and  the  multiformity  of  animal 


82         INFECTIOUS  AND  PARASITIC  DISEASES. 

life  never  cease  to  excite  the  admiration  and  wonder  of 
the  traveler.  While  from  the  temperate  zone,  in  a 
direction  away  from  the  equator,  vegetable  and  animal 
life  grows  less  and  less  abundant  and  flourishes  for  a 
briefer  period  of  each  year,  as  we  approach  the  frigid 
zones.  These  diversities  in  climate  have  given  origin 
to  forms  of  life  peculiar  to  themselves,  and  attention  is 
directed  to  this  most  obvious  phenomenon  because 
similar  influences  play  their  part  in  the  production  of 
disease  the  world  over.  The  living  agents  of  disease 
are  either  animal  or  vegetable,  and  are  therefore  sub- 
ject to  the  same  physical  laws  as  govern  forms  higher 
than  they.  Just  as  there  are  plants  and  animals  indig- 
enous to  the  several  regions,  so  do  we  find  pathogenic 
agents  in  one  region  that  are  not  encountered  in  another. 
Likewise,  as  many  plants  native  to  temperate  zones 
outgrow  in  size  and  color  all  semblance  to  the  original 
when  cultivated  under  tropical  atmospheric  conditions, 
so  do  certain  diseases  common  in  temperate  latitudes, 
where  they  are  relatively  mild,  assume  in  the  tropics  a 
virulence  that  makes  of  them  a  terrible  scourge.  But 
here  the  simile  of  flora  and  fauna,  and  disease,  ends. 
Tropical  plants,  unless  carefully  nurtured,  do  not 
prosper  when  transplanted  in  temperate  climates; 
whereas  tropical  diseases  do,  if  circumstances  are  the 
least  propitious,  when  they  are  introduced.  The 
microscopic  agents  of  disease  are  less  sensitive  in  some 
respects  to  physical  agents  than  plants,  and  moreover 


PHENOMENA  OF  INFECTION.  83 

are  capable  of  ready  adaptation  to  new  environment. 
Conquest,  improved  methods  of  travel,  and  shorter 
routes,  have  brought  the  tropics  to  the  very  doors  of 
Western  nations,  with  the  result,  that  in  the  great 
commercial  benefits  accruing  from  easy  intercourse, 
there  has  come  a  menace  in  the  guise  of  disease.  Here 
and  there  tropical  diseases  have  already  been  introduced, 
and  while  the  number  of  such  instances  is  insignificant, 
and  they  have  been  successfully  combated,  it  has  excited 
alarm.  And  well  might  it!  Europe  has  a  number 
of  times  been  over-run  with  Oriental  plagues.  Up  to 
the  present  these  problems  have  been  dealt  with  chiefly 
in  those  countries  where  such  diseases  prevail,  but  who 
can  say  when  from  a  single  imported  case  a  herculean 
task  in  sanitation  and  preventive  medicine  will  not 
confront  some  nation  ?  In  temperate  latitudes,  tropical 
heat  is  seasonable  for  one  or  more  months  each  year, 
a  time  during  which  the  way  is  open  for  the  spread  of 
an  exotic  disease.  This  danger  the  nations  are  cogni- 
zant of,  and  special  commissions  are  investigating  such 
diseases  in  those  regions  where  they  are  endemic. 
Whenever  anything  is  discovered  which  bids  fair  to 
prove  valuable  as  a  preventive,  it  is  at  once  given  a  prac- 
tical test,  since  it  is  obvious  that  the  only  real  safe-guard 
the  peoples  of  temperate  climates  have  against  foreign 
diseases,  is  to  stamp  them  out  in  their  home-country. 
All  of  the  nations  have  likewise  founded  schools  of 
"Tropical  Medicine,"  where  the  etiology  and  sanitary 


84         INFECTIOUS  AND  PARASITIC  DISEASES. 

control  of  tropical  diseases  are  studied,  and  where  the 
same  is  taught  to  physicians  and  nurses  whose  duty 
it  may  be,  at  some  time,  to  cope  with  them. 

An  ever  present  danger  to  both  natives  and  foreigners 
in  tropical  countries  is  intestinal  diseases.  The  climatic 
conditions  predispose  to  congestion  of  the  abdominal 
viscera,  which  predisposes  the  latter  to  infections. 
Even  in  the  absence  of  infectious  agents,  chronic 
engorgement  may  give  rise  to  lasting  injury  in  one  or 
another  organ.  The  liver  is  the  organ  commonly 
affected  in  this  way,  a  chronic  enlargement  with  result- 
ing torpidity  in  functioning,  frequently  making  the 
unfortunate  sufferer  an  invalid  for  life.  Lay  writers, 
particularly  English  authors,  have  long  recognized  this 
affliction,  and  very  properly  held  it  responsible  for 
many  disagreeable  traits  of  character.  The  enlarged 
liver  of  the  retired  East  Indian  official  so  often  referred 
to  by  Thackeray,  is  therefore  not  a  mere  creation  of 
the  novelist's,  but  founded  upon  fact.  But  the  chief 
interest  for  us  in  the  congestion  of  the  viscera  due  to 
intense  heat,  is  in  the  fact  that  it  predisposes  to  a  host 
of  infectious  and  animal  intestinal  parasites  with  which 
the  tropics  abound.  Nearly  all  of  these  agents  get  into 
the  body  through  the  drinking-water,  or  from  eating 
raw  fruits  and  vegetables,  and  the  infectious  disorders 
which  they  excite  are  either  of  the  intestines,  or  the 
intestines  and  liver.  The  commonest  infectious  disease 
of  the  tropics  is  dysentery,  of  which  there  are  two 


PHENOMENA  OF  INFECTION.  85 

varieties,  namely,  (i)  bacillary  dysentery,  due  to  a 
bacillus  (bacillus  dysentericE,  Shiga),  the  other,  (2) 
amoebic  dysentery,  due  to  the  amoeba  dysenterice,  an 
animal  organism.  Next  in  importance  to  these  infec- 
tions are  various  disorders  resulting  from  animal  para- 
sites. By  exercising  great  caution  in  the  matter  of  food 
and  drink,  one  may  avoid  the  infectious  and  parasitic 
intestinal  disorders,  if  he  cannot  those  solely  dependent 
upon  climate.  From  the  latter,  too,  it  is  not  impossible 
to  escape,  if  one  abstains  entirely  from  alcoholics  and 
other  excesses  which  tend  to  increase  the  amount  of 
blood  in  organs  already  overfilled,  and  if  occasional 
visits  to  cooler  climates  be  made.  The  most  rigid 
adherence  to  the  laws  of  health,  combined  with  such 
as  are  especially  adapted  to  a  hot  country,  must  be 
followed.  These  measures  if  carried  out,  and  provided 
the  individual  is  free  from  disease  in  the  beginning, 
will  ensure  the  same  average  health  in  a  tropical  as  in 
a  temperate  country. 

The  degree  of  warmth,  the  amount  of 
Physical  moisture,  and  the  physical  conditions  of  a 
Conditions,  country,  all  have  a  bearing  upon  predis- 
position, because  they  supply  an  essential 
environment  for  the  perpetuation  of  forms  of  life  which 
either  cause  disease,  or  transmit  it.  Besides  the  vege- 
table micro-organisms,  bacteria  and  moulds,  there  are 
other  microscopic  and  larger  forms  of  life  belonging  to 
the  animal  kingdom  which  produce  disease.     Among 


86         INFECTIOUS  AND  PARASITIC  DISEASES. 

these,  protozoa,  the  lowest  form  of  animal  life,  are  of 
prime  importance.  Then  there  are  flukes,  worms, 
and  insects.  Of  the  pathogenic  protozoa  known, 
nearly  all  depend  upon  suctorial  insects  for  transmission 
from  one  person  to  another.  The  role  of  insects  in 
the  production  of  disease  is  large,  forming  a  highly 
important  branch  of  medicine;  and  it  is  destined  to 
become  much  larger.  Two  kinds  of  transmission  of 
pathogenic  micro-organisms  by  living  agents  are  recog- 
nized, (i)  in  which  the  insect  is  merely  an  accidental 
carrier  of  the  micro-organism;  (2)  in  which  the  insect 
acts  as  host  for  the  micro-organism  during  one  phase 
of  its  life-cycle.  Where  the  insect  is  an  accidental 
carrier  of  the  microbe,  the  surface  of  its  body,  or  its 
excrement,  has  been  contaminated  by  feeding  upon 
infectious  material.  Under  such  circumstances  a 
disease  is  transmitted  either  through  the  soiling  of  a 
wound,  or  through  the  contamination  of  an  article  of 
diet.  While  living  upon  the  insect  no  increase  in 
numbers  of  the  pathogenic  agent  takes  place.  Bac- 
terial (and  possibly  a  few  protozoan)  diseases  are  fre- 
quently transmitted  in  this  way.  In  a  previous  chapter 
the  wide-spread  prevalence  of  typhoid  fever  in  the 
United  States  military  camps  during  the  Spanish- 
American  war  was  mentioned  to  illustrate  the  trans- 
mission of  bacteria  by  flies.  Besides  flies,  ants,  bed- 
bugs, fleas,  and  ticks,  may  also  accidentally  carry 
bacteria,  and  besides  typhoid  fever,  insects  are  believed 


PHENOMENA  OF  INFECTION.  87 

to  transmit  at  times  other  bacterial  diseases  such  as 
Asiatic  cholera,  bubonic  plague,  leprosy,  tuberculosis, 
small-pox,  etc. 

But  where  an  insect  acts  as  host  for  a  pathogenic 
agent,  an  entirely  different  condition  is  presented.  Here, 
while  the  contamination  of  the  host  is  accidental  in  so 
far  as  the  latter  is  concerned,  it  is  a  necessary  sequence 
on  the  part  of  the  pathogenic  agent.  Agents  of  this 
class  are  alternately  parasitic  upon  human  beings  and 
insects.  Upon  each  host  a  supplementary  develop- 
ment begun  in  one  is  continued  in  the  other.  In  no 
other  way  can  growth  from  egg  to  adult  (life-cycle)  be 
accomplished.  In  addition  to  this  remarkable  pro- 
vision, each  agent,  through  the  workings  of  a  fixed  bio- 
logical law,  is  peculiarly  restricted  to  especial  hosts 
without  which  it  cannot  develop.  It  follows,  therefore, 
that  the  propagation  of  diseases  by  insect-hosts  is 
absolutely  contingent  upon  the  presence  of  that  partic- 
ular species  of  insect  which  is  the  agent's  natural  host. 

Hosts  may  belong  to  the  class  of  suctorial  (biting) 
insects,  or  to  such  as  are  likely  to  get  into  our  food  or 
drink.  One  instance  of  a  disease  due  to  a  protozoan 
which  is  transmitted  by  an  insect  (mosquito),  is  fur- 
nished by  malarial  fever;  another,  by  sleeping-sickness 
(trypanosomiasis),  of  which  the  African  stinging  fly 
glossina  is  the  host. 

Among  larger  organisms  which  themselves  produce 
pathological  conditions  are  insects,  flukes,  worms,  etc. 


88         INFECTIOUS  AND  PARASITIC  DISEASES. 

Most  of  these  have  as  yet  a  circumscribed  distribution, 
so  that  the  diseases  which  they  cause  are  hmited  to 
certain  regions.  Examples  of  such  diseases  are  parasitic 
haemoptysis  (pulmonary  distomiasis),  which  is  found 
almost  exclusively  in  China,  Japan,  and  Formosa; 
bilharziosis  (endemic  or  Egyptian  haematuria),  pre- 
vailing particularly  in  Egypt,  North  Africa,  Arabia  and 
Persia;  hook-worm  disease  (ankylostomiasis,  uncin- 
ariasis), common  in  Porto  Rica,  Southern  United  States, 
the  Philippine  Islands  and  Egypt ;  guinea- worm  disease 
(dracontiasis),  occurring  principally  in  Africa,  East 
Indies,  and  Panama.  These  examples  suffice  to  show 
the  relationship  between  insects  and  disease  on  the  one 
hand,  and  regions  and  insects,  upon  the  other.  It  is 
because  the  physical  characteristics  in  so  large  a  measure 
determine  the  insect  and  animal  life  of  a  country  that 
we  include  them  among  the  predisposing  causes  of 
disease. 

In  tropical  and  sub-tropical  countries  many  more 
diseases  are  due  to  animal  infectious  agents,  and  animal 
parasites,  than  in  temperate  latitudes,  and  larger 
numbers  of  both  agents  are  transmitted  by  insects. 
This  fact  again  emphasizes  the  danger  to  the  peoples 
of  temperate  climates  in  that  either  pathogenic  parasites 
themselves,  or  their  insect-hosts,  may  be  imported  dur- 
ing the  period  of  greatest  heat  and  moisture,  find  the 
conditions  propitious  for  multiplication,  and  sow  their 
virus  promiscuously.     Moreover,  a  few  may  become 


PHENOMENA  OF  INFECTION.  89 

acclimated  and  survive  the  cold  of  the  winter  months, 
breed  fresh  generations  the  following  summer,  and  in 
this  way  establish  a  new  endemic  focus  for  the  diseases 
which  they  carry. 

A  good  example  of  an  insect  which  acts  as  host  for 
an  infectious  animal  micro-organism,  and  one  which 
depends  for  existence  upon  the  physical  conditions  of  a 
country,  is  found  in  the  species  of  mosquito  (anopheles) 
which  transmits  malarial  fever.  As  the  anopheles 
only  breeds  in  shallow  puddles  of  water  or  slowly 
moving  streams,  it  is  manifest  that  w^ll-drained  regions 
are  likely  to  be  free  from  malaria,  while  those  presenting 
an  opposite  condition  are  favorable  to  its  introduction. 
This  same  species  of  mosquito  neither  breeds  nor  bites 
when  the  temperature  is  below  68  Fahrenheit,  a  fact 
which  explains  the  constant  presence  of  ague  in  tropical 
climates.  High  altitudes,  and  mountainous  regions, 
because  they  do  not  present  the  physical  conditions 
necessary  for  the  multiplication  of  the  anopheles,  are 
free  from  malarial  fever;  but  the  same  is  not  true  for 
yellow  fever,  which  is  transmitted  by  another  species 
of  mosquito,  the  stegomyia  fasciata.  This  species 
breeds  in  rain-spouts,  cisterns,  and  small  collections 
of  water  about  a  household.  Given  a  favoring  climate, 
therefore,  where  the  practice  of  storing  water  about 
dwellings  prevails,  there  is  no  reason  why  this  pestif- 
erous insect  cannot  become  domesticated  in  regions 
that   are   now   outside   the   yellow   fever   zones.    An 


90         INFECTIOUS  AND  PARASITIC  DISEASES. 

illustration  of  the  altitude  the  stegomyia  may  reach  is 
furnished  by  the  history  of  yellow  fever  in  Mexico,  as 
reported  by  the  U.  S.  Public  Health  and  Marine- 
Hospital  Service.  A  commission  from  this  Service, 
called  Working  Party  No.  i,  found  this  mosquito  at  an 
altitude  of  4200  feet  above  the  sea  level,  an  ascent  which 
they  ascribe  to  a  shortening  of  the  time-distance 
between  coast  and  interior  by  the  building  of  a  railroad. 
That  season  and  disease  are  related  phe- 

Season.  nomena  has  already  been  included  in  our 
discussion  of  climate.  It  only  remains  to 
illustrate  the  relationship.  Yellow  fever  is  a  disease 
of  tropical  countries,  and  of  sub-tropical  regions  during 
the  warm  months;  typhoid  fever  occurs  everywhere 
chiefly  in  the  autumn  and  early  winter  months. 

The  effect  of  season  upon  disease  is  strikingly  shown 
if  we  compare  the  two  extremes  of  the  year,  summer  and 
winter.  The  heated  term  is  characterized  by  diseases 
affecting  the  intestinal  tract,  the  cold  and  blustry 
months,  by  affections  of  the  respiratory  organs  and 
joints. 

Fasting,  poor  food,  unhygienic  surround - 
Fasting,  ings,  etc.,  are  potential  factors  in  the  pro- 
PoorFood,  duction  of  infectious  diseases.  They  all 
Etc.  conduce  to  a  low  state  of  the  vital  forces; 

and  an  impoverished  body  falls  an  easy 
prey  to  the  pathogenic  agents.  Nor  are  the  effects 
of  other  agencies  grouped  in  our  chart  under  environ- 


PHENOMENA  OF  INFECTION.  91 

ment  dissimilar  in  their  action.  Previous  disease, 
alcoholism,  injuries,  and  operations,  all  portend  the 
same  end,  viz.,  a  lessening  of  the  natural  resistance. 
The  blood  and  its  cells  contain  the  largest  amounts 
of  those  active  principles  which  combat  disease,  and 
when  it  wastes,  as  it  does  in  every  disorder,  this  func- 
tion is  depressed  or  suspended.  Besides  being 
''thinned"  by  disease,  the  blood  suffers  impoverishment 
through  poisons  (e.g.,  alcohol,  lead);  through  the 
absence  of  either  sufficient  or  nourishing  food;  through 
unhygienic  surroundings,  and  by  actual  loss  in  volume 
and  cellular  constituents  in  haemorrhages  consequent 
upon  operations  and  injuries,  and  also  blood  sucking 
parasites.  In  unhygienic  surroundings  perhaps  the 
most  potent  evil  is  the  absence  of  pure  air  (oxygen)  in 
sufficient  amounts  to  meet  the  normal  needs  of  the  body. 
Typhoid  fever  furnishes  a  remarkable  example  of  the 
predisposing  influence  of  a  disease.  After  an  attack 
of  typhoid,  a  person  is  particularly  prone  to  diseases 
of  the  biliary  passages,  such  as  inflammation  of  the 
gall-bladder  (cholecystitis)  and  gall-stone  formation 
(cholelithiasis).  Predisposition  is  brought  about  in 
the  following  way:  During  the  fever,  typhoid  bacilli 
find  their  way  into  the  gall-bladder,  where  they  are 
liable  to  remain  for  months  and  even  years,  and  besides 
constituting  a  nidus  there  for  the  formation  of  gall- 
stones, may  also  at  any  time  give  rise  to  either  a  catar- 
rhal or  suppurative  inflammation  of  this  organ. 


92         INFECTIOUS  AND  PARASITIC  DISEASES. 

That  occupation  has  a  pronounced  influ- 
OccuPATioN.  ence  upon  longevity  is  well  illustrated  by 

the  comparative  mortality  table  appended. 
Comparative  mortality  of  men  twenty-five  to  sixty- 
five  years  of  age,  in  different  occupations,  1881  to  1883 
(Ogle): 

Comparative 
Occupation.  Mortality. 

Clergymen,  priests  and  ministers 100 

Lawyers 152 

Medical  men 202 

Gardeners 108 

Farmers 114 

Commercial  clerks 179 

Innkeepers^  liquor  dealers 274 

Inn^  hotel  service 396 

Brewers 245 

Butchers 211 

Bakers 172 

Tailors 189 

Book-binders 210 

Builders,  masons,  brick-layers , 174 

Carpenters 147 

Plumbers,  painters,  glaziers 216 

Blacksmiths 175 

Cotton  manufacture 196 

Cutler,  scissor  maker 229 

File  makers 300 

Glass  workers 214 

Earthen-ware  workers 314 

Coal  miners 160 

Stone,  slate  quarries 202 

Street  hawkers 338 


PHENOMENA  OF  INFECTION.  93 

The  laws  of  nearly  all  the  States  take  cognizance  of 
the  dangerous  character  of  certain  occupations  by 
specifying  the  safe-guards  under  which  work  of  this 
nature  is  to  be  done,  and  penalizing  disobedience. 
They  further  recognize  that  many  occupations  are  not 
in  themselves  so  injurious  to  health  as  the  unhygienic 
condition  of  the  surroundings,  the  crowded  states  of 
the  work-shops,  and  the  long  hours  imposed.  Sweat- 
shops exhibit  in  the  highest  degree  the  evils  just  referred 
to. 

The  predisposing  influence  of  an  occupation  may  be 
exerted  locally  upon  some  organ,  as  the  lung,  or  upon 
the  body  generally.  Thus  pulmonary  tuberculosis  is  of 
frequent  occurrence  in  persons  whose  occupations  are 
carried  on  in  an  atmosphere  of  dust  peculiar  to  their 
trades,  e.g.,  stone-cutters,  file-grinders,  cutlers,  cut- 
glass  grinders,  etc.,  a  danger  which  can  be  diminished 
by  placing  suction  hoods  above  the  field  of  work. 
Not  all  dust,  however,  is  equally  harmful,  a  difference 
demonstrated  in  the  case  of  coal  miners  who,  while 
breathing  in  a  dust-laden  atmosphere  day  after  day 
for  years,  are  not  markedly  predisposed  to  tuberculosis. 
Another  example  of  the  predisposing  influence  of  occu- 
pation upon  an  organ  is  found  in  seamstresses,  who, 
on  account  of  the  attitude  assumed  while  working, 
are  predisposed  to  ulcer  of  the  stomach. 

Occupations  which  create  a  general  predisposition 
are  those  in  which  the  worker  is  either  subjected  to  the 


94         INFECTIOUS  AND  PARASITIC  DISEASES. 

action  of  poisons,  or  in  which  the  tension  of  the  work 
is  a  §evere  strain  upon  the  nervous  system.  Some 
poisons  per  se  produce  pathological  states,  e.g.,  lead, 
arsenic,  mercury,  etc.  These  also  tend  to  the  produc- 
tion of  an  impoverished  state  of  the  blood  (anaemia), 
constipation,  etc.,  abnormalities  which  we  already 
have  called  attention  to  as  paving  the  way  for  infections. 
Occupations  involving  severe  strains  disturb  the  nervous 
system,  which  in  turn  affects  the  nutrition  and  func- 
tions of  every  part  of  the  body. 

In  Ogle's  table  illustrating  the  comparative  mortality 
in  the  various  occupations,  innkeepers  and  liquor 
dealors  are  seen  to  head  the  list  in  point  of  frequency. 
This  is  not  because  there  is  anything  especially  injurious 
in  the  occupation,  but  because  the  occupation  usually 
leads  to  excessive  indulgence  in  intoxicants.  So  well 
recognized  is  this  association  of  alcoholism  with  the 
handling  or  sale  of  liquors,  that  life  insurance  com- 
panies universally  regard  individuals  of  this  class  as 
bad  ^^ risks"  and  refuse  to  insure  their  lives. 

The  incidence  of  age  and  disease  is  well 
Age.  established.  There  are  disorders  of  in- 
fancy, of  childhood,  of  adolescence,  and 
of  old  age.  Middle  life  also  has  its  afflictions  in  the 
way  of  special  diseases,  but  as  we  are  limited  to  in- 
fectious diseases,  and  they  are  not  associated  to  any 
marked  extent  with  this  period,  the  affections  peculiar 
to  it  will  not  be  discussed. 


PHENOMENA  OF  INFECTION.  95 

The  young  infant  is  remarkable  in  its 
Infancy,  comparative  freedom  from  the  infectious 
diseases  of  childhood.  During  late  foetal 
life  the  unborn  child  may  suffer  from  a  large  number 
of  infectious  diseases  which  perchance  attack  the 
mother,  and  many  instances  are  on  record  of  infants 
being  born  with  typhoid  fever  and  small-pox;  indeed 
the  foetus  has  been  known  to  survive  an  attack  of  small- 
pox and  be  born  with  a  scarred  face,  a  circumstance 
which  attended  the  birth  of  the  great  obstetrician, 
Mauriceau.  To  measles  and  scarlet  fever,  and  even 
such  a  virulent  infection  as  yellow  fever,  the  infant  up 
to  the  sixth  month  and  often  longer,  is  practically 
immune;  the  same  is  true  of  typhoid  fever  and  other 
exanthemata;  yet  to  small-pox  it  is  highly  susceptible. 
From  one  infection  in  particular  should  the  new- 
born be  protected,  namely,  erysipelas  of  the  umbilical 
cord,  a  disease,  as  we  have  seen,  which  has  great  danger 
in  it  for  the  mother  also.  Another  infection  for  which 
the  umbilical  cord  is  a  portal  of  entry  is  tetanus,  an 
accident  fortunately  not  often  encountered.  It  occurs, 
however,  sporadically  in  a  few  localities  where  the 
bacilli  are  numerous  in  the  ground,  and  then  among 
the  poorest  and  least  cleanly  of  the  people. 

At  the  time  of  birth,  if  the  mother  is  suffering  from 
gonorrhoea,  the  infant  is  liable  to  three  localizations  of 
this  disease,  viz.,  in  the  mouth  and  conjunctivae  of  the 
eyes,  and  in  females,  in  the  vulva  also.     Gonorrhoeal 


96         INFECTIOUS  AND  PARASITIC  DISEASES. 

conjunctivitis  (ophthalmia  neonatorum)  is  a  very 
serious  infection,  and  requires  prompt  treatment  if 
the  sight  is  to  be  saved.  From  sixty  to  seventy  per 
cent  of  all  blindness  in  the  world  has  been  caused 
by  it.  Happily,  loss  of  sight  may  be  guarded  against 
by  dropping  one  drop  of  a  i  per  cent  solution  of  ni- 
trate of  silver  between  the  parted  lids  of  each  eye, 
at  birth,  in  all  infants  born  of  mothers  who  are  not 
above  suspicion;  indeed,  nearly  all  maternity  hospit- 
als and  out-patient  departments  make  this  a  routine 
procedure. 

Gonorrhoea  of  the  vulva  is  also  a  serious  affection. 
Very  few  vaginal  discharges  in  children  have  any  other 
origin.  The  disease  is  not  only  important  because  it 
may  affect  the  child  in  after  years,  but  also  because  it 
may  cause  death  from  peritonitis  by  extension  of  the 
infection  to  the  peritoneal  cavity. 

To  the  end  of  the  second  year  diarrhoea  in 
Childhood,    summer,    and    respiratory    infections    in 

winter,  are  the  principal  diseases.  From 
the  second  year  to  puberty  is  the  period  of  greatest 
susceptibility  to  scarlet  fever,  measles,  chicken-pox, 
mumps,  whooping-cough,  and  diphtheria.  These  years 
embrace  the  period  of  childhood,  and  on  account  of 
the  preponderance  of  the  above  mentioned  diseases 
during  this  time  the  latter  are  called  the  ^'diseases  of 
childhood."  Diseases  peculiar  to  children  exhibit  such 
variations  from  the  same  or  other  diseases  seen  in  later 


PHENOMENA  OF  INFECTION.  97 

life  as  to  have  given  rise  to  specialists.     The  specialty 
is  called  pcBdiatrics. 

Besides  the  general  infectious  diseases,  children  are 
more  predisposed  to  infections  of  the  lymphatic  glands 
and  bones  than  adults.  The  glands  most  frequently 
affected  are  those  of  the  neck  (cervical) ;  and  the  infec- 
tious agents  are  either  the  tubercle  bacillus,  or  the 
common  pus  cocci.  Inflammation  of  bone,  osteomy- 
elitis, is  also  a  frequent  affliction  of  childhood.  The 
thigh  and  lower  leg  are  the  most  likely  sites  for  infec- 
tious foci.  In  this  affection  the  tubercle  bacillus,  and 
the  pyogenic  cocci,  are  again  the  common  cause.  The 
unsightly  deformity  of  hunchback  (Pott's  disease), 
and  the  lesser  evil,  hip- joint  disease,  are  also  examples 
of  the  localization  of  the  tubercle  bacillus  in  bone. 

Young  adults  still  exhibit  some  suscepti- 
bility  to  the  diseases  of  childhood,  but  in  a 

CENCE.  -^ 

much  lessened  degree.  However,  at  this 
period  susceptibility  is  principally  shown  towards  two 
wide-spread  diseases,  pulmonary  tuberculosis  and 
typhoid  fever.  Predisposition  to  the  former  is  almost 
entirely  the  result  of  heredity  and  environment;  to 
the  latter  it  appears  that  age  is  the  most  important 
contributing  factor. 

Pneumonia  is  the  commonest  infectious 
Old  Age.    disease  of  the  declining  years  of  life,  and 

the  principal  cause  of  death.  In  men, 
prostatic   enlargement   frequently   interferes  with   the 


98         INFECTIOUS  AND  PARASITIC  DISEASES. 

voiding  of  urine,  a  condition  which  itself  predisposes  to 
inflammation  of  the  bladder  (cystitis).  Often  there 
is  such  obstruction  that  ''catheter-life"*  is  necessarily 
resorted  to,  with  the  result  that  infection  sooner  or 
later  occurs.  This  per  se  is  not  immediately  dangerous 
to  life,  although  the  intermittent  pyrexia  (fever),  and 
the  continuous  discharge  of  pus,  sap  the  patient's 
strength.  Subsequently  symptoms  of  toxaemia  develop 
either  through  extension  of  the  inflammation  to  the 
kidneys  or  from  absorption,  or  from  both  causes. 
Death  finally  takes  place  from  an  intensification  of 
the  toxaemia,  or  from  bacteriaemia.  Pulmonary  tuber- 
culosis is  also  encountered  in  old  persons,  and  may 
also  be  a  cause  of  death.  Besides  these  affections, 
there  are  practically  no  others  to  which  a  person  beyond 
sixty  years  is  predisposed.  Occasionally  measles 
attacks  a  patriarch,  and  sometimes  typhoid  fever,  but 
such  instances  are  exceptional. 

*  The  condition  in  which  a  catheter  is  always  employed  when  the 
bladder  is  to  be  emptied. 


CHAPTER    IV. 
INFLAMMATION. 

The  changes  which  take  place  in  a  tissue  when 
injured,  and  all  those  changes  which  follow  as  a  con- 
sequence of  the  injury,  constitute  inflammation.  In 
previous  chapters  emphasis  was  laid  on  the  fact  that 
the  body  resents  injury  and  is  quick  to  battle  against 
any  agent  which  tends  to  do  it  harm;  also,  that  it  pos- 
sesses remarkable  reconstructive  ability  when  des- 
truction of  tissues  has  occurred.  Both  the  defensive 
and  reconstructive  powers  of  the  body  are  due  to  what 
was  termed  its  "defensive  mechanism,"  a  function 
that  has  grown  to  its  present  proportions  through  the 
operation  of  natural  laws  which  govern  survival  and 
development. 

We  have  seen  that  recovery  from  infectious  diseases 
is  due  to  the  neutralization  of  the  toxic  products  of 
bacteria,  or  solution  of  the  bacteria  themselves  by  sub- 
stances (antibodies)  which  are  formed  within  the  body. 
The  action  of  antibodies,  however,  is  limited  either  to 
the  neutralization  of  toxins  or  bacteria,  since  they 
neither  repair  injured  tissues  nor  replace  those  destroyed. 
In  simple  injuries  from  mechanical  and  physical  causes, 

99 


loo       INFECTIOUS  AND  PARASITIC  DISEASES, 

and  also  in  some  inflicted  by  many  chemical  and 
animate  ones,  antibodies  are  not  created,  because  the 
toxins  which  stimulate  their  production  are  wanting. 
In  such  instances  the  reactions  excited  at  the  site  of  the 
injury  suffice  to  counteract  the  action  of  the  damaging 
agent  and  repair  the  tissues  affected.  But  when  infec- 
tious agents,  and  also  certain  poisons  e.  g.,  snake  venom, 
produce  injuries,  then  both  antibodies  and  local  defen- 
sive phenomena  are  brought  into  action.  Hence  the 
defensive  mechanism,  it  will  be  observed,  has  a  dual 
action;  one,  to  produce  antibodies;  the  other,  to  repair 
tissues  injured  and  destroyed.  The  process  of  repair 
is  characterized  by  entirely  different  phenomena  than 
those  of  antibody  formation,  albeit  both  often  arise 
from  the  same  source,  viz.,  injury  to  cells.  This  differ- 
ence is  illustrated  by  the  fact  that  while,  on  the  one 
hand,  the  formation  of  antibodies  is  conducted  by 
cells  situated  at  a  distance  from  the  lesion,  repair,  on 
the  other,  is  a  process  which  involves  the  lesion  itself 
and  neighboring  cells.  For  the  process  of  repair  the 
name  inflammation  is  used,  and  under  it  are  included 
all  immediate  and  subsequent  changes  in  a  tissue  or 
organ  that  has  sustained  an  injury. 

If  it  were  our  purpose  to  treat  inflammations  ex- 
haustively, we  should  have  to  take  into  consideration 
the  various  agents  which  produce  bodily  injuries,  and 
every  tissue  and  organ  susceptible  of  injury;  also  such 
local  and  general  conditions  of  the  body  as  influence 


INFLAMMATION.  loi 

the  process  in  one  way  or  another.  Furthermore, 
because  pathogenic  agents  differ  so  greatly  in  the 
reactions  which  they  excite,  and  different  tissues  re- 
spond so  variously  to  the  same  or  different  pathogenic 
agents,  we  would  be  led  into  a  description  of  every 
form  of  inflammation,  both  acute  and  chronic — a 
study  that  would  not  end  until  almost  the  whole  domain 
of  pathological  anatomy  would  have  been  explored. 
But  such  is  not  our  purpose.  There  are  certain  fun- 
damental phenomena  which  characterize  every  inflam- 
mation which,  while  they  represent  the  primary  reactions 
to  injury,  are,  at  the  same  time,  preliminary  to  repair. 
These  we  propose  to  explain.  Besides,  the  evolution 
of  inflammations  in  general  presents  special  features 
which  permit  us  to  point  out  the  protean*  character  of 
the  process  without  committing  us  to  a  lengthy  dis- 
cussion. 

Four  so-called  cardinal  symptoms  of 
Cardinal        •   n  ^-  i  •      i 

mnammation  are  commonly  recomized, 
Symptoms  of     .        ,  ,  ,,.  ,         . 

VIZ.,    heat,    redness,    swelhng    and    pam. 

,r*^,^.^  To  these  a  fifth  is  added  by  some  authors. 

MATION.  ,  ^  ' 

interference  with  function.  The  phenom- 
ena which  underlie  these  symptoms  are  as  follows: 
Redness  is  due  to  a  dilatation  of  the  adjacent  blood 
vessels;  swelling,  to  the  increased  calibre  of  the  blood- 
vessels, and  to  blood-serum  and  blood-cells  which  have 
passed  out  from  the  walls  of  the  former  into  the  sur- 

*  Assuming  different  forms. 


I02       INFECTIOUS  AND  PARASITIC  DISEASES. 

rounding  tissues.  Pain  is  due  to  tension  and  pressure 
exerted  on  neighboring  nerve-endings;  heat  to  the 
fact  that  there  is  both  an  increased  amount  of  blood 
in  the  part,  and  because  metabohsm  is  locally  quickened. 
Since  the  nutrition  of  a  part  is  obviously  disturbed  by 
inflammatory  phenomena,  there  is  no  need  to  dwell 
on  the  associated  disturbance  of  function.  Dilatation 
of  blood-vessels,  exudation  of  serum,  and  migration 
of  blood-cells,  are  therefore  the  body's  initial  response 
to  injury  (local  reactionary  phenomena),  and  are  pres- 
ent in  the  beginning  of  inflammation. 

The  earliest  stage  of  inflammation,  congestion,  is 
not  considered  beyond  the  borderland  of  health,  indeed 
it  is  the  normal  physiological  state  of  a  tissue  or  organ 
when  active.  When,  however,  serum  has  escaped  into 
the  tissues  (effusion),  this  boundary  has  been  passed, 
although  the  part  may  return  to  normal  without  loss 
of  substance  through  absorption  of  the  exudate  by  the 
veins  and  lymphatics.  An  exudation  is  protective 
to  the  body  from  infection  both  through  its  germicidal 
powers  and  by  dilution  of  toxins. 

Among  the  early  phenomena  of  inflam- 
Leucocytes.   mation  is  the  escape  of  cellular  elements 

from  the  blood-vessels.  These  cells  con- 
sist of  both  red  blood-corpuscles  and  larger  colorless 
cells,  called  leucocytes.  There  are  many  varieties 
of  leucocytes  in  the  blood,  but  probably  only  two  or 
three  of  these  have  a  share  in  the  inflammatory  process. 


INFLAMMATION.  103 

Those  concerned  are  capable  of  independent  move- 
ment, and  make  their  exit  from  the  capillaries  by 
insinuating  themselves  between  the  cells  which  line 
the  capillary  walls.  The  fenestra  which  they  open 
close  again,  but  not  quickly  enough  to  prevent  the  escape 
of  a  few  of  the  red  cells.  Once  beyond  the  vessel- 
walls  the  movements  of  leucocytes  are  determined  by  a 
mysterious  force  exerted  by  the  infectious  agents. 
This  force  (chemotaxis)  either  attracts  (positive  chemo- 
taxis),  or  repells  them  (negative  chemotaxis). 

Negative  chemotaxis,  however,  is  only 
Chemotaxis.   active  so  long  as  the  agent  is  present,  for 

on  the  cessation  of  the  agent's  action,  or 
its  elimination,  leucocytes  return  and  take  up  their 
specific  functions.  In  inflammatory  conditions  the 
leucocytes  have  several  offices  to  perform;  they  carry 
off  the  debris  of  injured  cells,  and  any  foreign  matter 
introduced  when  the  injury  was  sustained;  they  also 
destroy  by  digestion  invading  bacteria;  a  third  ofhce 
is  to  take  part  in  the  formation  of  new  tissue.  In  the 
last  instance  they  are  actually  converted  into  grow- 
ing tissue  cells.  Metchnikoff,  a  distinguished  bacteriol- 
ogist, who  is  our  greatest  authority  on  the  place  of 
leucocytes  in  inflammation,  contends  that  they  are  also 
largely  concerned  in  the  production  of  immunizing 
substances  (antibodies).  Be  this  as  it  may,  it  is  plain 
that  the  leucocytes  are  exceedingly  valuable  factors 
in  inflammations. 


I04       INFECTIOUS  AND  PARASITIC  DISEASES. 

The  most  important  function  of  leucocytes 

in  local  and  general  inflammations  is  to 
TOSIS.         ,  ,  ?  .  ,.,.,. 

destroy  bacteria,  an  action  which  is  desig- 
nated   phagocytic  J    the    function    itself,    phagocytosis. 
In    almost    every  inflammatory  condition 
of  the  body  the  number  of  leucocytes  in 

TOSIS.  -^  •' 

the  blood  is  increased.  Normally,  there 
are  about  6000  of  all  kinds  to  the  cubic  centimeter, 
but  50,000  to  60,000  are  not  unusual  in  inflammations. 
When  present  in  numbers  above  7000,  a  leucocytosis 
is  said  to  be  present.  The  explanation  of  this  increase 
of  leucocytes  in  the  blood  is  found  in  the  large  numbers 
required  at  inflammatory  foci.  In  the  discharge 
from  an  abscess,  for  example,  there  are  present  4  to  5 
millions  per  cubic  centimeter.  The  additions  made 
to  the  normal  number  of  leucocytes  in  the  blood  are 
due  to  the  stimulated  activity  of  the  blood-forming 
(hematopoietic)  organs  which,  as  occasions  arise, 
verily  surcharge  the  blood  with  them.  Whence  comes 
the  stimulus  ?  Obviously  from  absorption  of  a  prod- 
uct formed  at  the  site  of  the  injury.  Leucocytosis 
is  therefore  another  phenomenon  which  should  impress 
upon  us  the  deep-seated  reactions  occasioned  by 
every  injury,  whether  the  latter  gives  rise  to  general 
symptoms  or  not,  and  how  far  parts  of  the  defensive 
mechanism  are  placed  from  the  injury.  In  injuries 
due  to  mechanical  and  physical  agents,  when  not  com- 
plicated by  invading  bacteria,  the  succeeding  inflam- 


INFLAMMATION.  105 

mations  follow  an  orderly  progress  to  repair;  exuda- 
tions are  absorbed,  dead  cells  and  their  debris  are 
removed  by  the  phagocytes  and  connective  tissue  cells, 
and  either  connective  tissue  cells  or  cells  peculiar  to  the 
organ  or  tissues  involved  take  the  place  of  those  removed. 
But  most  inflammations  are  not  of  this  nature,  being 
caused  or  complicated  by  bacteria  and  their  toxic 
products.  The  first  effect  of  the  latter  is  the  same  in 
all  cases,  viz.,  to  excite  the  cardinal  phenomena  of  in- 
flammation; from  this  point,  however,  the  further  prog- 
ress and  termination  of  the  process  is  determined  by 
the  interaction  of  three  forces: 

1.  The  nature  and  intensity  of  the  invading  agent. 

2.  The  tissue  or  tissues  in  which  the  bacteria  are 
localized. 

3.  The  local  and  general  resistance  of  the  individual. 

Thus  the  same  micro-organism  (streptococcus  pyog- 
enes) which  on  a  mucous  membrane  can  produce  a 
false  membrane,  may  in  the  subcutaneous  tissues 
give  rise  to  an  abscess,  or  to  gangrene;  or  if  the  local 
resistance  is  not  sufficient,  will  invade  the  blood  and 
cause  a  bacteriaemia.  Another  bacterium,  the  tuber- 
cle bacillus,  produces  usually  tumor-like  growths  in 
tissues,  but  it  often  causes  rapid  necrosis,  and  not  in- 
frequently pus. 

Here  it  may  be  well  to  direct  attention  to  the  fact 
that  in  infectious  diseases  the  inflammatory  process 
is  not  confined  to  a  single  locality  or  organ;  but  since 


io6       INFECTIOUS  AND  PARASITIC  DISEASES. 

either  the  bacteria  or  their  toxins,  or  both,  are  dissem- 
inated throughout  the  body,  such  parts  are  affected  as 
are  susceptible  to  their  action,  and  in  these  inflamma- 
tions are  excited. 

If  early  subsidence  of  the  primary  phenomena  of  an 
inflammation  does  not  take  place,  necrobiosis  of  greater 
or  lesser  degree  follows :  in  those  instances  where  some 
cell  destruction  was  the  starting  point  for  the  phenom- 
ena, there  is  extension  of  the  necrobiotic  area.  Viewed 
from  the  stand-point  of  tendency,  inflammations 
are  either  destructive  or  constructive,  that  is  to  say, 
some  exhibit  an  immediate  tendency  to  disorganization 
of  tissues,  other  to  organization.  However,  to  say 
that  the  tendency  of  an  inflammation  is  destructive 
does  not  contradict  what  has  been  said  of  the  general 
purpose  of  inflammations,  viz.,  defense  and  repair. 
A  microbe  enters  a  wound  in  the  skin, 

or  by  way  of  the  blood,  the  tissues  of  some 
Suppuration.  .       -^     ,  ^-  ,  ,  .  ,.      . 

mternal    organ.     Through    multiplication 

and  the  excretion  of  toxins  a  focus  of 
necrosis  is  established.  Coincidentally  with  the  for- 
mation of  this  focus  the  cardinal  signs  of  inflammation 
have  made  their  appearance,  and  so  performed  their 
part  that  the  necrobiotic  area  is  circumscribed  by  a 
wall  of  leucocytes  which  act  as  a  barrier  against  deeper 
invasions.  Beyond  the  leucocytic  wall,  connective 
tissue  cells  are  in  active  process  of  proliferation  pre- 
paratory to  encroaching  upon  the  necrotic  area  as  it  is 


INFLAMMATION.  107 

eliminated.  Suppose  the  invading  microbe  belongs 
to  a  species  which  causes  suppuration.  The  next 
stage  in  this  form  of  inflammation  would  then  be  lique- 
faction of  the  dead  cells  by  ferments,  and  rupture  of 
the  fluid  contents  through  the  skin.  Gradual  enlarge- 
ment of  the  opening  often  permits  a  '^core^^  of  dead 
tissue  not  yet  liquefied  to  be  extruded.  The  material 
escaping  from  such  a  lesion  is  pus,  and  consists  chiefly 
of  large  numbers  of  leucocytes  suspended  in  serum  and 
liquefied  tissues.  In  this  discharge  are  also  eliminated 
bacteria  and  toxins.  Leucocytes  give  pus  its  creamy 
consistency  and  yellow  color.  The  dead  tissue  having 
thus  been  gotten  rid  of,  healing  goes  on  through  growth 
of  connective  tissue  cells  and  contraction  (cicatrization). 
The  above  is  a  description  of  the  formation  and  course 
of  an  abscess. 

Suppuration  under  natural  conditions  is  practically 
always  due  to  bacteria — a  single  exception  among 
animal  infectious  agents  being  the  amoeba  of  dysen- 
tery, which  is  known  to  cause  abscess  of  the  liver. 
There  are  a  number  of  bacteria  which  cause  suppura- 
tion; some  habitually,  some  specifically,  and  others  acci- 
dentally. The  common  members  of  these  three  groups 
are  as  follows: 

I.     Pyogenic  Bacteria. 
Staphylococcus  pyogenes  aureus. 
Staphylococcus  pyogenes  citreus. 
Staphylococcus  pyogenes  albus. 


io8       INFECTIOUS  AND  PARASITIC  DISEASES. 

Streptococcus  pyogenes. 
Micrococcus  tetragenus. 
Bacillus  pyocyaneus. 

2.     Specific  Pyogenic  Bacteria. 
Diplococcus  intracellularis  meningitidis. 
Gonococcus. 
Bacillus  of  glanders. 
Bacillus  of  bubonic  plague. 

3.     Accidental  Pyogenic  Bacteria. 
Bacillus  of  anthrax. 
Bacillus  of  tuberculosis. 
Bacillus  of  influenza. 
Bacillus  of  typhoid  fever. 

Suppuration  is  one  example  of  a  destructive  inflam- 
mation; gangrene  is  another. 

When  the  inflammatory  phenomena  are  not  too 
intense,  the  connective  tissue  cells  tend  at  once  to 
organize  about  the  area  of  injury  and  repair  it.  They 
form  what  are  called  infectious  nodules.  This  type 
of  inflammation  is  represented  by  syphilis  and  tuber- 
culosis, and  illustrates  the  antithesis  of  suppurative 
inflammations  in  its  immediate  tendency  to  repair. 


CHAPTER  V. 
ANIMAL  PARASITES. 

Man  is  host  for  numerous  animal  parasites  both 
large  and  small.  A  parasite,  we  have  seen,  is  ''an 
organism  which  lives  upon  another  organism  called  the 
host."  Parasites  may  live  permanently  upon  their 
hosts,  or  be  only  temporary  inhabitants.  They  may 
have  their  habitat  upon  the  exterior  of  our  body,  when 
they  are  called  ecto- parasites;  or  within  it  {endo-para- 
sites).  All  human  ecto-parasites  are  either  mites 
(arachnida),  or  true  insects;  all  endo-parasites  belong 
to  the  protozoa,  trematoda,  cestoda,  or  nematoda. 

By  temporary  parasite  is  implied  an  organism  which 
seeks  the  human  body  for  a  single  meal  only,  and  passes 
for  the  next  to  a  new  host.  To  this  class  belongs 
mosquitoes,  bed-bugs,  ticks,  etc.  By  permanent  para- 
site is  understood  an  organism  which,  when  it  finds 
lodgment  upon  or  within  the  body,  remains  there 
until  dislodged  either  by  accident,  through  the  instru- 
mentality of  drugs,  or  because  the  host  is  no  longer  a 
suitable  pabulum  either  for  further  development  or 
for  a  continued  existence.  Death  of  the  host,  of  course, 
terminates  the  status,  parasitism.     Most  human  endo- 

109 


no       INFECTIOUS  AND  PARASITIC  DISEASES. 

parasites  are  remarkable  for  the  complicated  and  un- 
usual manner  by  which  they  attain  maturity;  indeed, 
it  is  owing  to  this  unusual  evolution  that  they  produce 
pathological  states.  Nearly  all  require  for  their  com- 
plete growth  at  least  two  hosts,  man  and  some  other 
creature,  in  each  of  which  complementary  stages  of 
development  take  place.  They  may  also  have  a  stage 
of  growth  in  water  or  in  the  ground.  Taken  together, 
the  progressive  development  of  a  parasite  from  egg  to 
adult  is  called  its  cycle.  Parasites  which  require  two 
hosts  to  complete  their  cycle  may  pass  these  in  hosts 
which  are  biologically  allied,  as  for  example,  the  beef 
and  pork  tape-worms,  whose  hosts  other  than  man  are 
respectively  implied  in  their  names.  Often,  however, 
the  dissimilitude  in  hosts  is  truly  remarkable,  and 
causes  us  to  marvel  at  the  ingenuity  which  unraveled 
their  cycles.  Thus,  the  parasites  of  malaria,  yellow 
fever,  and  filariasis,  have  each  a  stage  of  development 
in  particular  mosquitoes;  the  guinea- worm,  in  a  water- 
flea;  the  schistoma  haematobium,  in  a  special  species 
of  snail.  The  examples  given  above  illustrate  a  curious 
phenomenon  in  regard  to  parasites  and  hosts  to  which 
there  are  few  exceptions,  viz.,  that  each  parasite  is 
restricted  to  hosts  which  enable  it  to  complete  its  cycle. 

Note: — For  a  fuller  description  than  is  given  here  of  animal  para- 
sites, well  illustrated,  the  general  reader  is  referred  to  Tyson's  "Prac- 
tice of  Medicine,"  4th  ed.;  or  numerous  articles  in  Woods'  "  Ref. 
Handbook  of  the  Medical  Sciences,"  last  ed. 


ANIMAL  PARASITES.  iii 

and  that  development  cannot  take  place  in  insects  and 
animals  which  do  not  have  this  relationship  to  the 
parasites.  One  illustration  will  suffice;  no  other 
mosquito  besides  the  genus  stegomyia  fasciata  can 
harbor  or  convey  yellow  fever,  and  none  besides  the 
genus  anopheles,  malaria.  In  the  stomach  of  other 
varieties  of  mosquitoes  than  anopheles  the  Plasmodia 
malaricE  are  digested. 

PROTOZOA. 

The  smallest  forms  of  animal  life  parasitic  upon  man 
belong  to  the  protozoa.  The  latter  constitute  that 
class  of  organisms  the  individuals  of  which  are  com- 
posed of  only  a  single  cell.  Like  bacteria,  all  parasitic 
protozoa  are  microscopic  in  size.  Their  structure, 
however,  is  far  more  complex,  and  their  life-cycle  is 
bizarre  in  the  extreme.  Thus,  some  are  known  to 
develop  partly  in  water  and  partly'  in  a  host;  others 
entirely  within  the  bodies  of  two  or  more  hosts. 

Those  which  have  part  of  a  cycle  in  water,  and  the 
other  in  man,  usually  gain  entrance  into  the  body  in  the 
drinking-water. 

Examples  of  this  class  are  found  in  the  amoeba  of 
dysentery  and  the  coccidium  hominis.  The  last  men- 
tioned is  probably  the  cause,  also,  of  that  peculiar  tumor 
known  as  epithelioma  contagiosum.  On  the  other 
hand,  in  the  case  of  such  varieties  as  never  reach  the 
external  world,  but  spend  their  whole  existence  in 
various  special  hosts,  these  are  usually  conveyed  to 


112        INFECTIOUS  AND  PARASITIC  DISEASES. 

man  by  one  of  their  hosts  which  itself  is  also  a  human 
parasite.  An  instance  of  the  latter  is  found  in  the 
malarial  plasmodium,  which  is  inoculated  by  the 
anopheles  mosquito. 

The  principal  human  protozoan  parasites  are  the 
amoeba  dysenterice,  the  trypanosoma  gambiense,  the  pro- 
tozoan of  Dum-Dum  fever,  and  the  Plasmodium  ma- 
laricB  (three  varieties). 

This  parasite  is  the  cause  of  an  acute  and 
Amceba  chronic  dysentery  principally 

Dysenteric.,  prevalent  in  Egypt,  India, 
and  tropical  countries  gen- 
erally, although  it  also  occasions  a  large 
proportion  of  the  cases  of  dysentery  in 
the  United  States. 

The  site  of  its  activity  is  the  large  intes-  co^Gr'^^^t^er 
tine,  the  mucous  membrane  of  which  it  Braun.) 
erodes  and  undermines  to  an  extent  seen  in  no  other 
malady.  The  organism  gains  entrance  into  the  body 
in  the  drinking-water  and  through  polluted  vegetables 
which  are  eaten  raw.  There  is  a  special  tendency  to 
abscess  of  the  liver  in  dysentery  of  amoebic  origin,  and 
perforation  of  the  abscess  through  the  diaphragm  into 
the  right  lung  is  a  not  uncommon  event.  In  appear- 
ance this  amoeba  is  not  unlike  the  white  corpuscles  of 
the  blood.  Harmless  amoebae,  however,  also  occur 
normally  in  the  stools  and  must  be  differentiated  from 
the  pathogenic  amoeba  histolytica. 


ANIMAL  PARASITES.  113 

Trypanosomiasis,  or  the  infestment  of  the 

blood  with  flagellated  protozoa,  trypano- 
Trypanosoma  .  .    . 

P  somes,  IS  common  among  many  varieties 

of  animals,  viz.,  fish,  birds,  horses,  cattle, 

etc.  In  some  it  is  productive  of  disease, 
in  others  not.  Different  varieties  of  trypanosomes, 
probably,  are  the  cause  respectively  of  the  disease  of 
horses  and  cattle  in  India  and  the  Philippine  Islands 
known  as  surra,  and  of  the  tsetse-fly  disease  or  nagana 
of  South  Africa.  In  man  the  parasite  is  associated 
with  the  dreadful  African  ^'Sleeping-sickness,"  and  is 
transmitted  by  the  stinging  fly  glossina. 

Dum-Dum  fever,  or  Tropical  Spleno- 
DuM-DuM  megaly,  is  a  protozoan  infection  prevalent 
Fever.  among  the  natives  of  India,  Assam,  Ceylon, 

China  and  Egypt.  The  parasite,  Donovan- 
Leishman  bodies,  has  been  found  widely  distributed 
in  the  body.     The  manner  of  transmission  is  unknown. 

Protozoa  which  increase  their  numbers 
Plasmodium  by  the  production  of  spores  or  seeds  are 
Malarle.       called  sporozoa.    When  sporozoa  live  at 

the  expense  of  the  red  blood-cells  of  an 
animal  they  are  especially  distinguished  by  the  signifi- 
cant name  hcemosporidia.  To  the  latter  class  belongs 
the  Plasmodium  of  malaria.  The  plasmodium  malariae 
(Laveran),  of  which  there  are  three  varieties,  lives  and 
develops  within,  and  at  the  cost  of,  the  colored  cor- 
puscles of  the  blood.    When  first  seen  it  appears  as  a 

8 


Description  of  Fig.  5. 

Life  history  of  malaria  parasite,  Plasmodium,  i,  Sporozoite,  intro- 
duced by  mosquito  into  human  blood,  the  sporozoite  becomes  a  schizont; 
2,  young  schizont;  3,  young  schizont  in  a  red  blood -corpuscle;  4,  full- 
grown  schizont;  5,  nuclear  division;  6,  spores,  or  merozoites,  from  a 
single  mother-cell;  7,  young  macrogamete  (female),  from  a  merozoite, 
and  situated  in  a  red  blood-corpuscle;  "ja,  young  microgametoblast 
(male);  8,  full-grown  macrogamete;  8a,  full-grown  microgametoblast; 
9,  mature  macrogamete;  ga,  mature  microgametoblast;  gh,  resting  cell, 
bearing  six  flagellate  microgametes  (male) ;  10,  fertilization  of  a  macro- 
gamete by  a  motile  microgamete;  the  macrogamete  next  becomes  an 
ookinete;  11,  ookinete,  or  wandering  cell,  which  penetrates  into  the  wall 
of  the  stomach  of  the  mosquito;  12,  ookinete  in  the  outer  region  of  the 
wall  of  the  stomach,  i.  e.,  next  to  the  body  cavity;  13,  young  oocyst, 
derived  from  the  ookinete;  14,  oocyst,  containing  sporoblasts,  which 
develop  into  sporozoites;  15,  older  oocyst;  16,  mature  oocysts,  con- 
taining sporozoites;  17,  transverse  section  of  salivary  gland  of  an  Anoph- 
eles mosquito,  showing  sporozoites  of  the  malaria  parasite  in  the  gland 
cells  surrounding  the  central  canal. 

^    1-6 .illustrate  schizogony  (asexual  production  of  spores);  7-16,  spo- 
rogony  (sexual  production  of  spores). 

(FoLSOM — After  Grassi  and  Leuckart,  by  permission  of  Dr.  Carl 
Chun.) 


114 


Fig.  5 


ANIMAL  PARASITES.  115 

small  irregular  colorless  body  within  the  red  blood-cell. 
This  body  increases  gradually  in  size  until  it  quite 
fills  the  cell.  As  it  grows,  pigment-granules  appear, 
which  at  first  are  peripherally  placed,  but  later  collect 
in  a  clump  in  the  center  of  the  parasite.  At  this  stage 
the  parasite  has  matured,  and  its  whole  body  splits 
up  into  spores,  or  new  young  parasites  which,  upon 
rupture  of  the  red  blood-corpuscle,  are  set  free  in  the 
blood  and  attach  themselves  to  fresh  cells.  In  an 
infected  person  large  numbers  of  plasmodia  appear  to 
reach  maturity  and  sporulate  about  the  same  time,  and 
it  has  been  found  that  the  chills  and  fever  correspond 
with  this  division  of  the  parasites. 

In  tertian  malarial  jever,  the  plasmodium  attains 
maturity  in  forty-eight  hours,  in  quartan  fever,  seventy- 
two  hours,  facts  which  seem  to  explain  the  regularity 
of  the  chills  in  these  two  forms  of  ague.  In  cBstivo- 
autumnal  fever  another  special  variety  of  parasite  is 
concerned  which  attains  maturity  in  from  twenty-four 
to  forty-eight  hours,  in  consequence  of  which  the  course 
of  this  form  of  ague  is  irregular. 

During  the  course  of  all  the  malarias  there  are  also 
formed  in  the  blood  oval,  spherical,  or  crescentic 
bodies,  some  of  which  are  flagellated,  others  non-flagel- 
lated. These  are  sexual  elements  of  the  parasites,  the 
flagellated  forms  constituting  the  males,  the  non-flagel- 
lated, the  females.  Union  of  these  in  the  blood,  how- 
ever, for  some  unknown  reason,  does  not  take  place, 


ii6       INFECTIOUS  AND  PARASITIC  DISEASES. 

but  in  the  stomach  of  different  species  of  mosquitoes 
of  the  genus  anopheles,  which  suck  up  the  malarial 
parasites  when  biting.  In  the  mosquito's  stomach, 
coalescence  (copulation)  of  the  sexual  elements  occurs 
and  a  new  organism  is  formed.  The  new  parasite  in 
turn  forms  other  organisms  in  large  numbers,  which 
pass  from  the  mosquito's  stomach  to  its  body-cavity 
and  thence  collect  in  its  salivary  glands ;  from  this  situa- 
tion they  find  their  way  into  the  blood  of  man  again  when 
the  insect  bites.  The  forms  thus  inoculated  give  rise 
to  malaria. 

It  has  been  definitely  proven  that  malarial  fever  can 
be  conveyed  in  only  one  way,  viz.,  through  the  bite  of  a 
mosquito  which  harbors  the  plasmodium,  and  that  only 
species  of  the  genus  anopheles  are  capable  of  acting 
as  host  to  this  parasite.  Clinically  the  pathological 
states  resulting  from  invasion  of  the  body  by  the  pro- 
tozoan parasites  above  described  are  not  unlike  those 
of  an  infectious  disease;  indeed,  we  regard  them  as 
belonging  to  the  latter  class,  and  would  therefore  include 
the  agents  which  cause  them  among  the  infectious 
agents.  They  are  placed  among  the  parasites  here 
simply  for  convenience  of  description. 

NEMATODES. 
FiLARiA  Or  guinea-worm,  is  a  round  worm  which 

Medinensis  develops  in  the  subcutaneous  tissues. 
(Dracunculus  Only  the  female  is  known.  The  worm  is 
medinensis).    ^^^^^^  jj^^^  ^^i^  stomach  probably  through 


ANIMAL  PARASITES. 


117 


drinkingwater  containing  small  aquatic  crustaceans 
{Cyclops  quadricornis)  which  themselves  harbor  the 
embryos.  The  embryos 
penetrate  the  intestinal 
wall,  reach  the  subcu- 
taneous tissues,  and 
there  attain  full  develop- 
ment. The  seat  of  elec- 
tion is  the  lower  ex- 
tremities, particularly 
about  the  heels,  yet  the 
parasite  has  been  found 
in  other  parts  of  the 
body.  It  is  said  that 
the  worm  can  be  felt 
beneath  the  skin  "like 
a  bundle  of  strings." 
When  the  worm  is  ma- 
ture it  breaks  through 
the  integument,  forming 
at  first  a  little  vesicle, 
later  a  small  discharg- 
ing ulcer,  and  from  the 

r     1        1                1  I^IG-  ^- — F'ilaria  medinensis;  a,  anterior 

bottom  of  the  latter  the  extremity;   O,  mouth;   P,  papillae;   h,  fe- 

\^r.r.A       r.^^^rs4-\^^r.r.      ^-^^  malc,  reducccl   to  less  than  half  normal 

head       sometimes      pro-  ^^ult  size;   c,  larv^,  enlarged.     (Braun, 

trudes.      Embryos    are  after  ciaus.) 
discharged  through  the  opening  in  the  skin,  more  par- 
ticularly when  water  is  applied.     After  getting  rid  of 


ii8       INFECTIOUS  AND  PARASITIC  DISEASES. 

her  larvae  the  worm  leaves  her  host  spontaneously.  The 
embryos  find  their  way  into  water,  often,  probably,  when 
the  host  is  bathing,  and  as  has  been  said,  develop  in  the 
water-flea  cy clops.  The  adult  worm  is  of  considerable 
size,  measuring  from  50  to  80  cubic  centimeters  (20-32 
inches)  in  length  and  a  few  millimeters  in  breadth.  It 
is  of  a  white  or  yellowish-brown  color.  When  the 
worm  begins  to  come  out  it  should  be  left  alone  at  first, 
as  it  may  leave  spontaneously.  However,  it  can  be  ex- 
tracted by  catching  the  protruding  head  between  the 
split  end  of  a  smooth  stick  and  winding  it  up  on  the  lat- 
ter, a  few  turns  a  day.  This  is  known  as  the  Soudanese 
method  of  extraction.  Care  should  be  taken  not  to 
break  the  worm  during  removal,  as  disastrous  conse- 
quences may  follow  rupture. 

The  guinea-worm  is  widely  distributed  in  tropical 
and  sub-tropical  countries,  but  occurs  most  frequently 
in  Africa,  Southern  Asia,  India,  and  Brazil.  In  places 
where  this  parasite  is  known  all  water  used  for  drinking 
purposes  should  be  boiled,  and  no  uncooked  vegetables 
should  be  eaten.  Also,  since  the  possibility  of  the 
worm  entering  the  skin  has  not  been  definitely  excluded, 
baths  should  be  taken  in  clear  water  only. 

Known  quite  generally  as  the  filaria 
T,  sanminis    hominis    lives,    as    its    name 

implies,  in  the  blood.  Only  the  embryos, 
however,  are  really  present  in  the  blood,  the  adult 
worms  having  their  habitat  in  one  of  the  larger  lymph 


ANIMAL  PARASITES.  119 

vessels  of  the  trunk.  The  mature  parasites  measure 
from  S;^  milhmeters  (male)  to  155  millimeters  (female) 
long,  by  5  millimeters  broad;  the  embryos  are  about 
the  diameter  of  a  red  blood-corpuscle  in  thickness  and 
about  30  times  as  long.  This  filarium  is  widely  dis- 
tributed, being  found  in  the  Southern  United  States, 
South  America,  India,  China,  Japan,  West  Indian 
Islands,  etc. 

The  most  important  lesions  resulting  from  the  para- 


Oh 


© 

Fig.  7. — Larval  filaria  hancrofti  in  blood.     (Coplin.) 


©-©  -  ©  ^^^'"^ 


Site  and  its  embryos  are  those  due  to  obstruction  of 
important  lymph  channels,  which  leads  to  a  hyper- 
plastic condition  of  the  tissues  of  the  parts  affected. 
On  account  of  the  huge  enlargement  of  the  parts,  and 
their  peculiar  varicose  appearance,  the  disease  is  called 
elephantiasis.  The  disease  is  never  general,  affecting 
only  either  one  or  both  legs,  the  scrotum  (lymph  scro- 
tum), one  or  both  labia,  or  a  breast,  etc. 


I20       INFECTIOUS  AND  PARASITIC  DISEASES. 

Filarial  embryos  are  looked  for  in  fresh  blood- 
specimens  the  same  as  for  malaria.  There  is  a  peculiar 
periodicity  about  their  appearance  in  the  peripheral  cir- 
culation in  the  respect  that  they  are  found  only  at  night. 

Mosquitoes  (culex)  act  as  intermediate  hosts  for 
these  filaria,  abstracting  the  embryos  from  one  person 
and  inoculating  them  into  others.  Persons  suffering 
from  filariasis  are  therefore  not  only  a  danger  to  them- 
selves (on  account  of  repeated  inoculations)  but  to 
others  who  may  chance  to  be  bitten  by  infested  mos- 
quitoes. In  man  again,  the  embryos  mature,  reach  a 
lymph  vessel  and  there  begin  producing  fresh  embryos. 

Hcematochyluria  is  also  caused  by  the  -filaria  san- 
guinis hominis.  However,  both  this  and  elephantiasis 
may  be  due  to  other  causes. 

Besides  the  above  filaria,  two  others  are  recognized 
by  Manson,  the  Filaria  diurna,  the  embryos  of  which 
are  found  in  the  peripheral  circulation  during  the  day- 
time only,  and  of  which  Manson  suspects  the  Filaria  loa 
to  represent  the  adult  worm,  and  the  Filaria  per s tans, 
which  the  same  author  regards  as  the  cause  of  a  skin 
eruption,  craw-craw,  found  on  the  west  coast  of  Africa. 
A  round  worm  of  whitish  or  yellowish 
Filaria  Loa.  color,  from  20  to  40  millimeters  (i  and  2 
inches)  in  length  by  3  to  5  millimeters  in 
breadth,  and  found  in  the  subcutaneous  tissues,  usually 
of  the  face,  but  more  especially  in  the  conjunctivae. 
Its  movements  in  the  skin,  which  are  visible  to  the  eye, 


ANIMAL  PARASITES.  121 

cause  considerable  itching  and  pain,  and  in  the  eye- 
hds  inflammation  and  swelling.  The  parasite  is  indig- 
enous to  the  western  coast  of  Africa,  and  is  of  common 
occurrence  among  the  natives. 

Both  Americans  and  Europeans  (chiefly  missionaries) 
have  harbored  filaria  loa  after  a  residence  in  Africa, 
and  had  them  removed  on  returning  to  their  respective 
countries.  Ward  records  the  history  of  seven  such 
cases  observed  by  physicians  in  various  parts  of  the 
United  States,  and  has  studied  the  specimens  in  a  few 
of  them.  He  concurs  with  Manson  in  the  opinion  that 
this  filaria  is  a  more  mature  form  of  the  Filaria  diuma.^ 
Removal  of  the  parasite  is  accomplished  by  grasping 
the  worm  firmly  through  the  cuticle  with  forceps,  and 
cutting  down  upon  it  with  scissors  or  knife.  Care 
should  be  taken  that  the  skinhold  on  the  worm  is  not 
loosened  until  the  worm  itself  is  grasped,  or  it  may 
escape  into  the  deeper  tissues.  The  embryos  of  the 
worm  are  believed  to  be  inoculated  into  man  by  an 
intermediate  host,  either  a  fly  or  mosquito.  Prophy- 
laxis in  filaria  loa  is  the  same  as  for  malaria. 

The  trichocephalus  dispar  (whip-worm)  is 
Trichiuris  a  common  parasite  of  the  intestinal  tract, 
Trichiura.  particularly  the  caecum.  Universally  dis- 
tributed, it  apparently  does  little  or  no 
harm,  although  anaemia  and  diarrhoea  have  occasionally 
been  ascribed  to  its  presence.     Both  the  worm  and  its 

*  See  Bui.  Univ.  of  Neb.,  January,  1906. 


122       INFECTIOUS  AND  PARASITIC  DISEASES. 

eggs   are   quite   characteristic   and   easily  recognized. 
The  hving  worm  is  seldom  found  in  the  stools. 
Strongy-        Occurs  in  the  stools  in  endemic  diarrhoea 
LoiDEs  of  hot  countries  (Cochin-China).     Has  also 

Intestin-        been  described  in  this  country  by  Thayer. 
ALis.  Infestment  only  produces  symptoms  when 

the  parasites  are  present  in  large  numbers.     Eggs  of 
the  parasites  are  probably  ingested  with  drinking-water. 
Trichiniasis,   as   infestment   of   the   body 
Trichinella  with  the  trichinella  spiralis  is 
Spiralis         called,  is  brought  about  by  eat- 
(Trichina        ing  insufficiently  cooked  or  raw 
spiralis).  meat  (usually  pork)  which  con- 

tains the  larval  forms.  The 
young  embryos  which  are  set  free  in  the 
stomach  by  digestion  of  their  capsules,  reach  g  _  . 
maturity  in  the  small  intestines  in  about  chiuHs  trichi- 
three  days.  The  females  then  give  birth  size':  .4,  male; 
to  innumerable  larvae — 8,000  to  10,000,  it  is  %ll^\^  ^' 
said — which  are  discharged  directly  into  the 
lymph  stream,  whence  they  finally  reach  the  blood  and 
are  distributed  to  their  points  of  election,  the  voluntary 
muscles.  Here  the  young  worms  become  encysted, 
i.e.,  each  one  arranges  itself  in  a  spiral,  and  becomes 
surrounded  by  an  inflammatory  capsule.  It  is  to  the 
encapsulation  of  the  embryos,  together  with  a  poison 
which  is  possibly  set  free  by  them,  that  the  symptoms 
of  trichiniasis  are  due. 


ANIMAL  PARASITES. 


123 


The  female  trichinella  is  a  fine  thread-like  worm 
measuring  from  3  to  4  millimeters  long;  the  male  is 
smaller,  measuring  1.5  millimeters,  and  has  two  little 
appendages  from  the  hinder  end  (bifid). 

Practically  all  domestic 


animals  may  act  as  host 
for  the  trichinella,  but  in- 
festment  in  man  is  seldom 
due  to  any  other  meat  be- 
sides pork.  The  disease 
occurs  wherever  pork  is 
eaten.  In  suspected  cases 
the  worms  should  be 
sought  in  the  stools,  or 
embryos  may  be  obtained 
by  removing  a  small  frag- 
ment of  the  pectoral  or 
biceps  muscle  under  local 
anaesthesia. 

If  pork  or  other  meats 
are  suspected  of  contain- 


FiG.   9. — Trichinella  spiralis.     En- 
capsulated  larva  in  muscle.     (Tyson 


ing  tnchinella,  the  latter  ^ft^^^raun.) 
may  be  easily  demonstrated  by  treating  a  thin  section  of 
the  tissue  with  a  solution  of  caustic  potash  (i-io)  and 
viewing  it  with  the  low-power  lens  of  a  microscope. 

Should  the  specimen  be  very  fat,  treat  it  with  ether 
or  dilute  acetic  acid  first  and  then  with  the  caustic 
potash  solution. 


124       INFECTIOUS  AND  PARASITIC  DISEASES. 


ASCARIS 
LUMBRI- 
COIDES. 


This,  the  common  round  worm  of  children, 

makes   its  home  in  the 

small  intestines  of   man. 
It    is    the   commonest 
human  parasite,  being  universally  dis- 
tributed. 

The  worm,  which  is  from  4-8  inches 
(male)  to  7-12  inches  (female)  in 
length  and  pointed  at  both  ends,  is 
transversely  striated  and  exhibits  four 
longitudinal  bands.  It  has  a  yellow- 
ish-brown or  reddish  color.  Usually 
the  host  harbors  only  a  few  adults — 
but  there  may  be  many.  The  eggs  of 
the  worm,  and  occasionally  an  adult 
parasite,  are  passed  in  the  stools. 

The  migrations  of  these  worms  are 
remarkable,  as  they  may  crawl  into 
the  stomach  and  be  vomited,  or  pass 
the  whole  length  of  the  oesophagus 
into  the  nose,  the  middle  ear,  or  the 
mouth.  They  have  frequently  been 
discovered  in  the  gall-bladder,  and 
have  also  been  known  to  cause  intes- 
tinal obstruction.  Ordinarily  symp- 
toms of  their  presence  are  absent,  or 
are  limited  to  minor  nervous  disturb- 
ances, such  as  irritability,  picking  at 


Fig.  10. — Ascaris 
lumhricoides:  to  left, 
male  in  lateral  aspect; 
to  right,  female,  ven- 
tral aspect,  natural 
size.  (Tyson  after 
Railliet.) 


ANIMAL  PARASITES.  125 

the  nose,  and  nocturnal  grinding  of  the  teeth.  How- 
ever, convulsions,  epileptiform  attacks,  vertigo,  and 
chorea,  have  also  been  described.  The  worms  are 
quickly  expelled  by  santonin  (gr.  J-i  for  child,  gr.  1-2 
for  adult)  given  either  alone  and  followed  by  the  same 
quantity  of  calomel  or  a  saline  purge;  or  equal  quanti- 
ties of  santonin  and  calomel  may  be  given  night  and 
morning  until  bowels  are  well  moved. 

The  parasite  is  contracted  from  water  or  food  con- 
taining the  ova,  so  that  a  host  may  not  only  convey  the 
parasites  to  others,  but  may  re-infect  hin^self. 

Also  known  as  the  pin-worm,  thread-worm, 
OxYURis     g^j^j  seat-worm,  has  its  habitat  in  the  caecum, 

colon  and  rectum.     It  is  a  very  common 

LARIS.  .  ^ 

human  parasite  the  world  over.  Found 
particularly  in  children,  there  is  no  period  in  life  when 
they  may  not  be  contracted. 

As  its  name  implies,  it  is  a  small  thread-like  worm 
from  4  millimeters  (male)- 10  millimeters  (female)  in 
length,  and  is  readily  seen  on  examination  of  the 
stools.  The  eggs,  which  are  also  passed  in  the  stools, 
are  probably  taken  into  the  stomach  with  water  or 
salads,  or  directly  from  the  contaminated  hands  of  the 
host. 

The  symptoms  occasioned  by  the  parasite  are  irrita- 
bility, nocturnal  restlessness,  and  itching,  particularly 
about  the  anus.  The  worms  may  leave  the  rectum  at 
night  and  deposit  eggs  on  the  perineum — or  in  females 


126       INFECTIOUS  AND  PARASITIC  DISEASES. 

may  invade  the  vagina.     They  have  been  found  in  the 
appendix. 

Treatment  is  with  santonin  as  in  infestment  with 
Ascaris  Lumbricoides,  and  the  daily  irrigation  of  the 
colon  with  strong  salt  water.  These  measures,  how- 
ever, do  not  always  effect  expulsion,  and  the  worms  may 
be  parasitic  for  years  despite  every  effort  to  dislodge 
them.  Self-pollution  may  be  responsible  in  some  cases, 
at  least,  for  the  obstinacy  with  which  they  resist  removal. 

The  Uncinaria  duodenalis  (strongylus 
Uncinaria  duodenalis,  anchylostoma  duodenalis,  hook- 
DuoDENALis.  worm),  is  a  parasitic  worm  which  has  its 

habitat  in  the  duodenum,  the  jejunum, 
and  occasionally  the  colon.     The  condition  to  which 


Fig.  12. — Tail,   with  expanded 
Fig.  1 1 . — ^Tail,  with  expanded  bursa,       bursa,  of  male  uncinaria  A mericana. 
of  male  uncinaria  duodenalis.  (Tyson.)       (Tyson.) 

it  gives  rise  is  known  under  as  many  names  as  the 
parasite,  viz.,  anchylostomiasis,  uncinariasis,  hook- 
worm disease,  Egyptian  chlorosis,  etc. 


ANIMAL  PARASITES.  127 

Infestment  is  common  in  both  the  Old  and  the  New 
World,  although  two  distinct  species  of  worms  are  con- 
cerned; the  Old-World  Uncinaria  duodenalis,  and  the 
New- World  Uncinaria  Americana.  The  disease,  which 
is  characterized  by  a  grave  anaemia,  and  in  untreated 
cases  has  a  large  mortality,  is  widely  distributed  in 
tropical  and  sub-tropical  countries.  There  are  also 
endemic  foci  in  temperate  climates.  The  island  of 
Porto  Rico  seems  to  suffer  more  from  this  parasite 
than  any  other  country,  one-fourth  of  the  total  deaths 
in  a  single  year  (1903)  having  been  ascribed  to  it.  The 
anaemia  prevalent  in  our  own  Southern  states  has  been 
demonstrated  by  Stiles  to  have  the  same  origin.  In 
temperate  climates,  infestment  is  common  in  tunnel- 
workers  and  miners. 

The  adult  worms,  which  jneasure  from  8-10  milli- 
meters (males)  to  12-18  millimeters  (females),  live  in 
the  small  intestines.  From  a  bending  backwards  of 
the  anterior  extremity  the  name  hook-worm  has  been 
derived.  They  are  blood-sucking  parasites,  and  by 
means  of  teeth  and  a  powerful  sucking  apparatus  attach 
themselves  to  the  mucous  membrane  lining  the  gut. 
A  few  parasites  do  not  cause  symptoms,  but  where  their 
numbers  are  large — in  many  cases  1000  or  more — the 
drain  upon  the  body  is  considerable,  often  ending 
fatally.  In  children  their  presence  interferes  with 
development.  Only  the  eggs  of  the  parasite  appear  in 
the  stools,  where  they  are  usually  present  in  enormous 


128       INFECTIOUS  AND  PARASITIC  DISEASES. 

numbers.  As  they  are  voided  in  process  of  segmenta- 
tion, they  are  easily  recognized  by  examining  a  drop  of 
feces  with  the  ordinary  powers  of  the  microscope. 
Hatching  takes  place  in  water  or  moist  earth,  situations 
in  which  the  embryos  may  live  for  months.  The  larval 
uncinaria  are  taken  into  the  body  in  the  drinking-water, 
or  from  the  hands  which  have  been  soiled  with  earth 
containing  them. 

(/Another  mode  of  entrance  is  through  the  skin.  The 
manner  in  which  they  get  into  the  bowels  is  interesting. 
From  the  skin  the  embryos  are  carried  to  the  right  side 
of  the  heart  and  to  the  lungs.  Here  they  escape  from 
the  pulmonary  vessels  into  the  air-spaces,  travel  up  the 
bronchi  and  larynx  into  the  oesophagus,  and  by  swallow- 
ing find  their  way  into  the  stomach  and  intestines.  It 
is  believed  that  the  tropical  skin  affection  known  as 
^^ground-itch,"  and  which  is  usually  confined  to  the 
ankles,  is  caused  by  the  entrance  of  embryo  uncinaria. 
In  the  duodenum  and  jejunum  full  development  is 
attained,  with  subsequent  reproduction  of  eggs.  The 
cycle,  it  will  be  observed,  is  direct. 

The  diagnosis  rests  upon  the  presence  of  eggs  in  the 
stools.  Stiles  calls  attention  to  the  value  of  the  blotting- 
paper  tests  for  blood  when  a  microscopic  examination 
cannot  be  made.  Reference  is  made  to  this  test  in  the 
chapter  dealing  with  the  examination  of  the  secretions 
and  excretions. 

Expulsion  of  the  parasites  is  ordinarily  successfully 


ANIMAL  PARASITES.  129 

accomplished  by  giving,  after  a  day  of  fasting,  two 
doses  of  thymol  (gr.  30  each)  in  brandy  or  whisky  two 
hours  apart,  and  two  hours  later  a  dose  of  castor  oil. 
If  ova  are  still  present  in  the  stools  a  few  days  later,  the 
same  treatment  should  be  repeated. 

Prophylaxis  consists  in  not  going  bare-footed  in 
regions  where  the  disease  prevails,  in  boiling  the  drink- 
ing-water, and  in  scrupulous  cleansing  of  the  hands 
before  meals.  The  stools  of  persons  harboring  the 
parasites  should  be  disinfected,  and  treatment  instituted 
in  all  cases  where  eggs  are  found  whether  symptom.s 
of  the  disease  are  present  or  not. 

FLAT  WORMS. 

Parasitic  flat  worms  are  divided  into  two  orders, 
the  trematodes  or  flukes,  and  the  cestodes  or  tape- 
worms. The  former  are  distinguished  by  possessing  a 
partial  digestive  canal  but  no  anus;  the  latter  by  a 
complete  absence  of  alimentary  tract. 

TREMATODES. 

Distomiasis  is  the  name  applied  to  diseases  resulting 
from  trematodes  or  flukes.  Flukes  are  mostly  small, 
flat,  leaf-shaped  worms,  which,  as  above  noted,  are 
without  anal  orifices.  Usually  they  possess  one  or 
more  suckers  and  occasionally  booklets.  They  are 
mostly  hermaphroditic.  Only  the  more  important 
varieties  will  be  referred  to. 
9 


I30       INFECTIOUS  AND  PARASITIC  DISEASES. 


This,  the  Asiatic  lung  fluke,  is  of  frequent 
Paragonimus  occurrence  in  human  beings  in  China, 
Japan,  Korea  and  Formosa,  causing  the 
disease  known  as  pulmonary  distomiasis 
or  parasitic  haemoptysis.     In  the  United 


(Distoma) 
Wester 

MANII. 


Fig.  13. — Paragonimus westermanii:  (ventral view).  ioXi--4>oral 
sucker;  B,  ceca;  D,  acetabulum;  E,  genital  pore;  F,  uterus;  G,  ovary; 
H,  testicles;  I,  vitelline  glands;  K,  excretory  canal;  L,  excretory 
pore.     (Braun,  after  Leuckart.) 

States  it  is  known  only  as  a  parasite  of  the  dog,  cat, 
and  hog.     The  adult  worm  is  from  8-10  millimeters  in 


ANIMAL  PARASITES.  131 

length  by  4-6  millimeters  in  breadth,  and  almost  as 
thick  as  broad.  It  is  of  a  pinkish  or  reddish-brown 
color.  Usually  the  worm  inhabits  the  bronchial  tubes 
of  the  animal  upon  which  it  is  parasitic,  but  it  has  been 
found  in  other  situations  also. 

The  symptoms  to  which  it  gives  rise  are  rarely  serious, 
consisting  of  a  chronic  cough,  and  a  rusty  (sanguineous) 
expectoration.  Occasionally  there  is  severe  haemopty- 
sis. Ova  of  the  parasites  are  found  in  the  expectora- 
tion, and  from  these  the  diagnosis  is  made.  Nothing 
is  known  of  the  manner  of  infestment.  Stiles  sounds  a 
note  of  warning  by  pointing  to  their  presence  in  domes- 
tic animals. 

LIVER  FLUKES. 

A  number  of  liver  flukes  occasionally  parasitic  in 
man  have  been  described,  of  which  one,  and  possibly 
two,  are  of  considerable  importance. 

Foremost  is  the  Chinese  or  Japanese  liver 
pisTHOR-     £^]^g^  Opisthorchis  sinensis,  which  is  com- 
SiNENsis       ^^^  ^^  China,  Japan,  and  India.     This 
species  is  somewhat  larger  than  the  lung 
fluke,  being  from  10-20  millimeters  in  length  by  2-5 
millimeters  in  breadth.     As  its  name  implies,  it  has  its 
seat  of  election  in  the  liver,  particularly  the  gall-pas- 
sages, and  gives  rise  to  digestive  disturbances,  jaundice, 
anaemia  and  dropsy.     Years  elapse  between  the  time 
of  infestment  and  death.     The  diagnosis  rests  on  the 
presence  of  eggs  in  the  stools. 


132       INFECTIOUS  AND  PARASITIC  DISEASES. 

Beyond  the  fact  that  the  eggs  will  develop  to  a  certain 
stage  in  water,  nothing  is  known  of  the  life-history  of 
this  parasite. 

Another  liver  fluke,  common  in  sheep ;  it  is 
Fasciciola  also  found  in  cattle,  hogs,  horses,  and 
Hepatica.       ruminants  in  general.     They  produce  in 

sheep  the  so-called  "  liver- rot."  The  worm 
is  a  frequent  parasite  of  animals  in  the  United  States. 
Few  cases,  however,  have  been  described  in  human 
beings  anywhere.  The  symptoms  of  infestment  are 
the  same  as  in  the  other  liver-fluke  diseases  already 
described.  The  eggs  of  the  parasite  are  found  in  the 
stools.  They  are  taken  into  the  body  probably  in 
water  or  upon  raw  salads. 

This  fluke  is  distinguished  from  other 
ScmsToso-  flukes  already  described  by  the  fact  that  it 
MUM  H^MA-   jg  ^^^^^  j^  ^^^  ^^^^^  particularly  the  por- 

TOBIUM  ,  .  1-11  rr^i  1. 

(B'lha   *  ^^^^  ^       ^^^  branches.     Ine  disease 

hfiematobia).  which  it  causes,  haemic  distomiasis,  Bilhar- 
ziosis,  or  Egyptian  haematuria,  is  prevalent 
in  Egypt,  Africa,  Persia,  and  the  west  coast  of  India. 
It  is  said  to  occur  in  Cuba  and  Porto  Rico  also.  Im- 
ported cases  are  occasionally  encountered  everywhere. 

In  this  fluke  the  sexes  are  separate.  The  eggs  of 
the  parasite  are  the  chief  cause  of  mischief. 

Symptoms  of  the  disease  are  practically  always 
referable  either  to  the  bladder  or  rectum.  In  involve- 
ment of  the  former  viscus  there  is  pain  and  burning  over 


ANIMAL  PARASITES.  i33 

the  supra-pubic  region,  irritability  of  the  bladder,  and 
hematuria;  in  the  latter,  straining,  tenesmus,  and  the 
passage  of  blood  and  mucus.  Ova  are  found  in  either 
discharge,  and  the  diagnosis  rests  upon  their  discovery. 
Haemic  distomiasis  is  a  very  important  disease,  as  its 
prevalence  in  many  countries  attests.  Since  communi- 
cation with  the  East  has  become  closer,  a  larger  number 
of  imported  cases  have  been  reported.  Dr.  Stiles  is 
of  the  opinion  that  the  United  States  will  suffer  from 
importation  of  parasites  by  troops  returning  from  foreign 
service  and  by  travelers.  The  same  author  leans  to 
the  belief  that  a  snail  acts  as  intermediate  host  for  the 
h^matobium.  If  this  be  true,  before  the  disease  can 
become  endemic  in  the  United  States  depends  upon 
*' whether  there  exist  in  the  United  States  species  of 
snails  which  can  serve  as  intermediate  hosts,  and 
whether  these  snails  actually  become  infected  by  persons 
harboring  the  parasite."  Furthermore,  if  snails  act 
as  intermediate  hosts,  then  "cases  of  infection  are 
more  likely  to  occur  in  rural  districts  than  in  cities, 
and  country  physicians  will  be  more  likely  to  encounter 

them''  (Stiles). 

CESTODES. 

Cestodes  or  tape-worms  are  flat,  segmented,  ribbon- 
like worms  which  have  their  habitat  in  the  small  intes- 
tines. They  are  characterized  by  a  complete  absence 
of  a  mouth  or  digestive  tract,  and  nourishment  is 
maintained  entirely  by  absorption  of  nutrient  material 


134       INFECTIOUS  AND  PARASITIC  DISEASES. 

through  the  external  covering.  Depending  upon  the 
species,  the  length  of  the  worm  varies  from  a  few  inches 
(dwarf  tape- worm)  to  thirty  or  more  feet  (Bothriocepha- 
lus  latus).  The  adult  worm  consists  of  a  head  or 
scoleXj  a  thin  thread-like  neck,  and  a  body  made  up 
of  conjoined  segments  or  proglottides.  The  head  is 
provided  with  suckers,  in  some  species  with  hooklets 
also,  by  means  of  which  the  worm  fastens  itself  to  the 
gut  and  maintains  its  position.  It  is  on  account  of  these 
organs  of  attachment  that  the  head  is  often  difficult 
to  dislodge.  Yet  it  must  be  expelled  if  a  cure  is  to  be 
effected,  since  growth  of  the  worm  proceeds  entirely 
from  the  head  end.  The  neck  is  unsegmented.  Behind 
the  neck,  the  first  segments  are  short  and  narrow,  but 
they  gradually  increase  in  size  until  the  adult  dimensions 
are  attained.  The  size  of  a  segment  is  related  to  its 
maturity. 

In  each  proglottidis  are  found  both  sexual  elements 
in  various  stages  of  development.  The  more  mature 
segments  are  situated  towards  the  distal  end  of  the 
worm  and  contain  numerous  ova,  in  each  of  which  is  an 
embryo  worm.  Segments  containing  embryos  are  said 
to  be  "ripe,"  and  it  is  these  which  are  constantly  sep- 
arating from  the  less  mature  and  being  shed  in  the 
stools.  When  they  appear  in  the  stools,  two  or  more 
segments  are  usually  found  attached  together.  These 
may  have  the  power  of  independent  locomotion,  a 
fact  which  should  not  mislead  the  observer  into  believing 


ANIMAL  PARASITES.  135 

that  they  constitute  a  whole  worm.  When  eggs  con- 
taining embryos  are  taken  into  the  stomach  of  a  suitable 
host — usually  in  water  or  food — the  embryos  are  liber- 
ated, pass  into  the  small  intestines,  the  walls  of  which 
they  penetrate,  and  reach  various  tissues  and  organs, 
the  liver,  muscle,  brain,  etc.  Here  they  become  encysted 
and  develop  into  cysticerci  or  '' bladder- worms,"  that 
is  to  say,  they  are  converted  after  a  few  months  into  a 
cyst  full  of  fluid.  From  a  point  on  the  inner  wall  of 
each  cyst  a  little  bud  projects,  which  in  time  is  converted 
into  a  tape- worm  head  or  scolex,  and  a  sac  containing 
it.  A  cyst  containing  a  tape-worm  head  is  known  as  a 
^^  measles  ^^  or  cysticercus  celhdosce.  Flesh  of  this  kind 
is  said  to  be  measled.  As  cysticerci  the  parasites  live 
indefinitely  until  the  flesh  containing  them  is  eaten  by 
another  host,  in  the  intestinal  tract  of  which  they  then 
grow  into  mature  tape-worms.  The  cycle  of  the  cestodes 
is  therefore  in  two  hosts,  with  possibly  a  short  interval 
between  spent  in  water.  Tape- worms  parasitic  in  man 
belong  to  two  orders — the  Tceniadce  and  the  Bothrio- 
cephalidcB.  The  first  occurs  in  man  either  as  ''measles " 
or  as  tape- worms,  the  latter  only  as  tape- worms.  Ten 
species  of  tape-worms  have  been  described,  of  which 
three,  only,  are  known  definitely  to  be  connected  with 
food.  These  are  Tcenia  saginata  (T.  mediocanellata) 
due  to  measly  beef,  Tcenia  solium,  to  measly  pork,  and 
Bothriocephalus  latus,  to  infested  fish,  such  as  sturgeon, 
pike,  perch,  and  salmon. 


136       INFECTIOUS  AND  PARASITIC  DISEASES. 


T^NIA  Sagi 
NATA  (T.  me- 


The  unarmed  or  beef  tape-worm  is  the  com- 
monest of  tape-worms  found  in  America, 
diocanellata)    ^^  inhabits  the  small  intestines.     In  length 
it  varies  between  9  and  24  feet.   The  head, 
which  measures  about  2  millimeters 
in  breadth,  is  pyriform  and  with- 
out   booklets,    but  contains    four 
cup-shaped  suckers  on  its  ventral 
aspect.      The    ripe   segments  are 
from  17-18  milhmeters  in  length 
by   8-10   millimeters    in    breadth. 
Cattle   act   as  intermediate  hosts, 
and  eating  uncooked  beef  contain-, 
ing  the  cysticerci  gives  rise  to  in- 
festment  in  man. 

Both  eggs  and  proglottides  are 
passed  in  the  stools.     The  proglot- 
tides are  easily  recognized  and  are 
diagnostic     of     an     adult     worm. 
Symptoms  due  to  tape-worms  may 
be  absent  entirely,  or  may  consist 
of  occasional  colic  and  an  abnormal 
appetite. 
Or  pork  tape-worm  is  a  rare  parasite  in 
the  United  States.     In  Europe  it  is  not 
uncommon.     It  is  a  smaller  cestode  than 
tcenia  saginata;  the  head  measures  less  than 
the  head  of  a  pin  (0.6-1  millimeter) ;  the  ripe  proglottides 


Fig.  14. — TcBnia  medi- 
ocanellata.  (Gould,  after 
Leuckart.) 


T^NIA 

Solium. 


ANIMAL  PARASITES. 


137 


are  10-12  millimeters  long  by  5-6  millimeters  broad; 
and  the  length  of  the  whole  worm  varies  between  6 
and  9  feet.  The  head  is  provided  with  four  suckers, 
and  a  double  row  of  booklets,  a  fact  from  which  has 
arisen  the  name  ''armed  tape-worm." 
The  ingestion  of  insufficiently  cooked 
'^measled"  pork  is  responsible  for 
infestment. 

Usually  only  a  single  worm  is  found 
in  one  individual,  but  more  may  occur. 
TcEiiia  solium  is  a  much  more  danger- 
ous parasite  than  tcenia  saginata  be- 
cause man  may  be  the  host  for  both 
the  adult  and  bladder- worms ;  on  this 
account  a  person  that  harbors  this 
parasite  should  be  especially  careful 
not  to  carry  a  soiled  hand  to  the  mouth 
or  allow  it  to  contaminate  food. 

The  adult  worm  per  se  gives  rise  to 
few  or  no  symptoms,  but  if  its  eggs 
are  ingested,  the  embryos,  besides  be- 
inff  distributed  to  muscles,  may  also     ^  ^.,   ,  . 

^  '  -^  Fig.   is.—Dtbothrw- 

find  lodgment   in  important  organs,  cephains  latus.  (Tyson, 

. ,       ,        .  1 .  ,  after  Leuckart.) 

e.g.,  the  bram,  eye,  hver,  etc. 

j^  This,  the  longest  tape-worm  met  in  man, 

cEPHALus  ^^  commonest  along  the  Baltic  Sea,  in 
Latus  (Both-  Japan,  and  in  Switzerland.  It  is  also  said 
riocephalus  to  be  of  frequent  occurrence  in  Munich, 
latus).  xhe  parasite  measures  from  6  to  30  feet 


138       INFECTIOUS  AND  PARASITIC  DISEASES. 


or  more  in  length.  The  head  is  narrow  transversely 
(0.71  millimeters)  and  differs  from  the  tcenia  in  having 
two  lateral  grooves  or  bothridia  as  suckers.  There 
are  no  booklets. 

Fish  act  as  intermediate  hosts  for  the  measles,  stur- 
geon, pike,  perch,  etc.  In  the  stools  of  a  person  harbor- 
ing the  bothriocephalus,  eggs  characteristic  of  the  worm 
are  found  in  large  numbers.  These  find  their  way 
into  water,  when  the  embryos  escape 
from  the  eggs  and  lead  a  free  existence  for 
an  unknown  period.  They  are  finally 
swallowed  by  their  fish-hosts,  from  whom 
man  in  turn  acquires  the  adult  worm. 

This  is  a  dog  tape- worm 
which  is  widely  distributed. 
Its  intermediate  hosts  are  the 
dog-louse  and  flea,  and  the 
ordinary  flea  of  man  {pulex  n^^^m 


Depylidium 
Caninum 
(taenia  cu- 
cumerina). 


Fig. 16 


Dipy- 
caninum. 

irritans).    Its   chief   interest  (Leuckart  after 

.      ,  1     1  •      -,  1  M  1  Weinland.) 

m  human  pathology  is  that  children  occa.- 

sionally  harbor  the  adult  worm,  contracting  it  from 

the  dog's  louse  or  flea. 

Known  also  as  the  '^ dwarf-tape- worm," 
Hymeno-  is  a  short  cestode  parasitic  in  rats, 
LEPsis  Nana,  mice,   and  man.     The  intermediate  host 

is  not  known.  The  worm  is  known 
throughout  Europe,  and  lately  many  cases  have  been 
reported   from   the   Southern   United   States    (Stiles). 


ANIMAL  PARASITES.  139 

Is  found  principally  among  the  very  poor.  When  many 
worms  are  present  they  may  give  rise  to  severe  symp- 
toms, and  may  even  be  a  cause  of  death.  The  adult 
worm  only  measures  from  10  to  15  millimeters  in  length. 
The  head  is  provided  with  four  suckers,  and  also  with 
a  single  row  of  booklets. 

VISCERAL  CESTODES. 

Whereas  adult  cestodes  which  inhabit  the  alimentary 
tract  occasion  as  a  rule  unimportant  symptoms,  local- 
ization in  various  organs  of  the  ''measles"  or  bladder- 
worms  may  be  a  very  serious  event.  Fortunately 
man  may  act  as  host  for  the  larval  forms  of  only  two 
tape- worms,  viz.,  Tcenia  solium  and  Tcenia  echinococ- 
cus;  and  more  fortunate  still,  such  infestment  is  not 
common. 

Or  ''measles,"  it  will  be  remembered,  is 
the  embryo  stage  of  Tcenia  solium  or  pork 

tape- worm.  Man  usually  harbors  the  adult 
Cellulosa.        ^     .  -'.  .  . 

parasite,  but  from  the  mgestion  of  ripe 

eggs  he  may  also  become  the  host  of  the 
larvae.  The  symptoms  of  infestment  depend  on  the 
localization  of  the  cysticerci.  Unless  a  vital  organ  is 
involved  they  may  be  trivial;  but  in  the  brain,  cord,  or 
eye,  serious  mischief  results.  In  a  few  cases  the  pres- 
ence of  subcutaneous  nodules  excited  suspicion,  which 
was  confirmed  by  removing  one  and  examining  with  the 
microscope. 


I40       INFECTIOUS  AND  PARASITIC  DISEASES. 


The  adult  form  of  this  cestode  is  found  in 
T^NiA  EcHi-  the  dog,  wolf,  jackals,  etc.  Man  harbors 
Nococcus.  the  larvae.  Infestment  is  practically  only 
encountered  where  dogs  are  kept  in  close 
relationship  with  their  masters,  as  in  Iceland  and 
Australia.     In    other    countries    sporadic    cases    are 

occasionally  reported,  usu- 
ally in  foreigners,  v/ho  prob- 
ably contracted  the  disease 
elsewhere.   The  adult  worm 
/f       P"^        WHW^     ^^  ^  ^^^^  cestode  from  2.5-5 
\\>       ^i       ^^BBW    ^^illii^^ters  in  length,  with 
V        flfel       ^Hfflllr       a  head  provided  with  four 

cup-shaped  suckers  and  a 
double  row  of  booklets. 
When  man  ingests  the  ripe 
ova  of  this  worm,  visceral 
infestment  {Echinococcus 
disease)  ensues.  Localiza- 
tion may  be  in  any  organ, 
the  liver,  lungs,  kidney, 
etc.  Huge  cysts  enclosing 
numerous  other  cysts  are 
stages  in  the  developraent  of 
the  embryos,  countless  numbers  of  which  may  develop 
from  a  single  (:^gg,  thus  differing  from  the  cysticercus  of 
other  cestodes  in  that  a  single  egg  gives  rise  to  only 
one  embryo. 


Fig.  17.  —  TcBnia  echinococcus: 
a,  adult;  h,  head  from  echinococcus 
cyst.  On  left  a  detached  hooklet, 
as  seen  in  fluid  from  cyst.  (Coplin 
and  Bevan,  after  Leuckart.) 


ANIMAL  PARASITES.  141 

INSECTS. 

Parasitic  diptera,  or  two-winged  flies, 
Parasitic  occupy  an  important  position  in  relation 
Diptera.  to  disease,  since  various  species  of  this 
order  are  harmful  to  man  in  a  number  of 
ways.  Besides  the  inconvenience  that  large  numbers 
of  diptera  cause  by  their  bites  (e.g.,  jigger- flea,  bed- 
bug, etc.),  incidents  which  are  not  always  unattended 
with  danger  to  health  and  life,  others  of  this  order  may 
burden  the  economy  with  their  young.  The  latter  is 
accomplished  in  one  of  two  ways:  i.  By  depositing 
their  eggs  or  larvae  either  upon  wounds  or  in  cavities 
(of  the  body)  leading  to  the  exterior,  such  as  the  nose, 
ears,  vagina,  etc.,  or  by  placing  them  beneath  the  skin. 
In  all  such  instances  the  larvae  feed  in  the  places  depos- 
ited and  cause  such  annoyance  as  their  growth  and 
migrations  excite. 

2.  In  other  instances  the  eggs  or  larvae  are  taken 
into  the  intestinal  tract  with  food  or  drink,  and  are 
voided  in  the  feces. 

Myiasis  is  the  technical  term  used  to  denote  the  con- 
dition in  man  in  which  the  larvae  of  diptera  are 
parasitic;  and  depending  upon  whether  the  larvae 
(maggots)  are  upon  the  exterior  or  interior  of  the  body 
it  is  designated  external  or  cutaneous,  and  internal 
myiasis,  respectively.  Where  maggots  are  found  in  the 
stools  care  must  be  taken  to  exclude  the  possibility  of 
flies  having  had  access  to  the  stools,  since  living  young 


142       INFECTIOUS  AND  PARASITIC  DISEASES. 

may  be  deposited  upon  them  by  the  latter.  Mosquitoes 
belong  to  the  two-winged  flies  or  diptera,  a  fact  which, 
if  previously  unknown  to  the  reader,  will  now  suggest  a 
third  way  in  which  these  insects  are  harmful,  viz., 
by  acting  as  secondary  hosts  for  other  human  parasites. 
Because  the  relationship  of  mosquitoes  to  malaria, 
yellow  fever  and  filariasis,  has  already  been  sufficiently 
elucidated,  additional  reference  to  them  here  would  be 
superfluous. 

Finally,  diptera  may  accidentally  convey  disease- 
agents  either  upon  their  bodies  or  in  their  feces,  factors 
in  disease  that  have  also  already  been  considered  else- 
where. 

To  the  (Estridas  or  bot-flies  belong  those  species 
the  larvae  of  which  are  parasitic  upon  man. 

Dermatobia    noxialis    Goudot.     This    fly 

GEsTRus        is  a  common  pest  in  tropical  America. 

HoMiNis.  Known  under  numerous  names,  viz.,  Ver 
macaque  (Cayenne  and  Mexico),  Ura 
(Brazil),  Torcel  (Costa  Rica),  its  larvae  are  deposited 
upon  exposed  portions  of  the  body,  whence  they  work 
their  way  into  the  subcutaneous  tissues.  Here,  if 
undisturbed,  they  complete  their  growth  and  issue  when 
mature  from  the  abscesses  to  which  their  presence  gives 
rise.  The  larvae  are  quite  characteristic  in  that  one 
end  (head)  is  quite  large  in  comparison  with  the  other, 
and  there  are  minute  spines  on  segments  two  and 
three. 


ANIMAL  PARASITES.  143 

The  larvae  of  this  fly  are  also  common 

lA 

Cyaniven- 


parasites.     They   are   distinguished   from 


TRis  ^^^  larvae  of  noxialis  by  having  no  fine 

spines  on  segments  two  and  three,  but  a 
row  of  strong  hooks  projecting  from  the  hind  margin  of 
segments  four  to  seven  (Blanchard). 

Compsomyia  macellaria  is  known  through- 
CoMPsoMYiA  out  America,  but  cases  of  myiasis  due  to  its 
Macellaria.  larvae  are  only  common  in  the  warmer  por- 
tions. The  larva  is  known  as  the  '^  screw 
worm."  The  bot-fly  itself  has  a  reddish-brown  head, 
a  bluish-green  thorax  and  abdomen,  and  the  thorax 
is  further  distinguished  by  three  longitudinal  black 
stripes.  The  eggs  are  deposited  upon  the  skin,  where 
they  quickly  hatch,  and  the  larvae  then  work  their  way 
into  the  subcutaneous  tissues  and  produce  abscesses. 
But  here  and  there  eggs  are  laid  in  the  nostrils  of  individ- 
uals asleep.  In  this  situation  the  growing  worms  pro- 
duce a  terrible  state  of  affairs,  since  in  their  burrowings 
they  may  destroy  all  the  tissues  of  the  soft  palate  and 
posterior  pharynx,  and  may  even  lay  bare  the  hyoid 
bone.  As  many  as  three  hundred  maggots  have  been 
discharged  from  the  mouth  and  nose  of  a  single  indi- 
vidual. 

This,  the  common  blue-bottle  or  flesh-fly, 
Sarcophaga   occasionally  lays  its  grubs  in  old  ulcers, 
Carnaria.       which  then  have  the  appearance  of  ^  liv- 
ing," that  is  to  say,  the  maggots  are  as 


144       INFECTIOUS  AND  PARASITIC  DISEASES. 

actively  motile  as  when  ordinarily  seen  in  decomposing 
material.  Solutions  of  bichloride  of  mercury  (i-iooo) 
quickly  rid  the  host  of  these  parasites. 

Or  common  flea  is  a  minute  red  or  dark- 
PuLEx  brown  insect  which  is  only  parasitic  upon 

Irritans.        man  in  countries  where  it  is  present  in 

great  numbers.     It  is  particularly  trouble- 
some in  hot  countries.     Its  eggs  are  not  laid 
in  the  skin,  but  in  cracks  of  floors,  sawdust 
and  dust.     Its  bites  are  irritating  and  may 
cause  wheals  (hives). 

The  sand-flea,  "jigger,"  "jig- 
Sarcopsylla  ger-fiea,"  "chigoe"  or  "chique" 
(pulex)  is  a  more  serious  parasite  than 

Penetrans,    the  common  flea.    The  impreg- 
nated female  burrows  into  the  skin  to  breed  ^  ^^^-  l^-  ~~ 

Larva  of  pu- 

her  young,  which  are  very  numerous.   Favor-  lex  irritans, 

1        ,  .  .  ,    (Gould.) 

ite  situations  are  the  lower  extremities  and 
feet,  particularly  beneath  the  nails  of  the  toes.  Painful 
swellings,  abscesses,  and  ulcers  often  result.  The  in- 
sect is  principally  found  in  Central  and  South  America, 
and  South  Africa.  The  fleas  may  be  picked  out  with 
a  needle,  but  one  should  be  careful  to  extract  them 
whole  since  distressing  sores  may  otherwise  result. 

Bed-bugs   are   true    cosmopolitans,  being 
CiMEx  found  the  world  over.     The  body  is  thin 

Lectularius.  and  flat   and  oval  in  outline.     Its  color 

varies  from  a  grey  to  a  dark  reddish- brown. 


ANIMAL  PARASITES. 


145 


It  has  a  characteristic  odor.  It  is  entirely  nocturnal  in  its 
habits,  sucking  blood  at  night  and  hiding  in  the  cracks 
of  the  bed,  of  cupboards,  etc.,  in  the  daytime.  This 
pest  can  usually  be  eradicated  from  beds,  etc.,  by 
washing  with  bichloride  of  mercury  (1-500),  pure 
carbolic  acid,  or  kerosene. 

Where  the  room  or  building  is  so  badly  infested  that 
these  measures  do  not  sufhce,  fumigation  with  sulphur 


Fig.    19. — Sarcopsylla   (pulex)   petietrans: 
young  female,  enlarged.     (After  Braun.) 


Fig.    20.  —  Bed-bug; 
I,  side  view;  2,  back  view. 


(i  pound  to  each  looo  cubic  feet  of  space)  is  a  reliable 
measure.  No  moisture  is  required  as  in  the  case  of 
fumigation  against  bacteria,  so  that  fabrics  are  not 
necessarily  injured,  and  the  exposure  need  not  be  longer 
than  two  or  three  hours. 

Pediculi  or  lice  are  found  chiefly  in  two 
Pediculi.      situations  on  the  body,  in  the  hair  of  the 
head  (pediculi  capitis),  and  in  the  pubic 
hairs  (pediculi  pubis  or  inguinalis). 


146       INFECTIOUS  AND  PARASITIC  DISEASES. 

Another  louse  is  found  in  the  seams  of  the  clothing 
(pediculus  vestimenti). 

This  is  usually  found  in  uncleanly  persons, 

Pediculus     but  may  accidentally  invade  the  fastidious. 

Capitis.         A  peculiarity  of  this  louse  is  that  its  color 

varies  v^ith  its  hosts,  that  is  to  say,  it  is 


Fig.  21. — Ovum 
of  head -louse  glued 
to  hair;  X70.  (Ty- 
son, after  Braun.) 


Fig.  22. — Pediculus  capitis.    X  ^S* 
(Tyson,  after  Braun.) 


light  grey  on  a  Caucasian,  yellowish  or  dark-grey  on  the 
Mongolian,  and  black  on  the  Negro.  The  individual 
lice  are  difficult  to  find,  but  their  presence  is  assumed 
by  finding  eggs  or  "nits."  These  are  little  oval  glisten- 
ing bodies  attached  to  the  hairs.  Treatment  consists 
in  cutting  the  hair  and  v^ashing  v^ith  kerosene. 


ANIMAL  PARASITES. 


147 


This  louse  is  commonly  known  as  the 
Pediculus  "crab-louse,"  from  its  resemblance  to  a 
Pubis.  crab.     Its  nits  are  attached  to  the  hairs 

quite  close  to  the  skin.  Oftenest  the  nits 
are  only  found  in  the  pubic  or  adjacent  hairy  parts, 
but  they  may  be  present  on  the  hairs  of  the  chest,  the 
axillae  and  even  on  the  eye-brows. 
Where  the  insect  bites,  a  minute 
slate-colored  lesion  results  which 
itches  intensely. 

The  parasite  is  ordinarily  con- 
veyed from  person  to  person 
during  sexual  congress,  but  sleep- 
ing with  a  person  harboring  the 
parasite  may  be  the  means  of 
contracting  it. 

The  "toilet"  has  also  been 
held  responsible. 

Both  the  parasite  and  its  nits 
are  quickly  killed  by  smearing 
the  affected  parts  with  mercurial  (blue)  ointment. 

The  clothes-louse  makes  its  home  in  the 
Pediculus  seams  of  the  clothing  and  underwear.  Its 
Vestimenti.  bites  cause  itching.  Scratch-marks  over 
the  back  and  around  the  waist-line  usually 
evidence  its  presence.  Boiling  or  steaming  the  cloth- 
ing, or  hot  ironing,  are  easy  means  of  ridding  a  person 
of  the  parasite. 


Fig.  23. — Pediculus  vesti- 
menti: X  io»  circa.  (Tyson, 
after  Braun.) 


148       INFECTIOUS  AND  PARASITIC  DISEASES. 

Or   Sarcoptes  hominis,   the   itch-mite,   is 
AcARus         another  parasitic  insect  which  forms  bur- 
ScABiEi         rows  in  the  skin.     Only  the  female  pro- 
(itch-mite).    duces  lesions,  the  purpose  being  the  depo- 
sition of  her  eggs.     The  portions  of  the 
body  selected  are  those  where  the  skin  is  thinnest,  viz., 
in  the  webs  between  the  fingers,  at  the  bend  of  the  elbows, 
in  the  axilla,  upon  the  penis,  at  the  bend  of  the  knees, 
and  about  the  ankles.     In  children,  burrows  may  be 
found  over  the  whole  body. 

Where  the  mite  penetrates  the  skin  a  little  vesicle  is 
formed,  and  the  direction  of  the  burrow  is  indicated 
by  a  rough,  dark  line.  However,  because  intense 
itching  always  accompanies  the  insect's  activity,  the 
only  lesions  discoverable  may  be  scratch-marks.  Itch- 
ing is  most  complained  of  at  night,  the  period  when  the 
female  is  active.  The  itch-mite  is  so  small  that  it  is 
seldom  seen  and  the  diagnosis  of  its  presence  is  made 
entirely  from  the  character  and  situation  of  the  lesions. 
It  is  of  historical  interest  that  the  first  Napoleon  was  a 
sufferer  from  ''itch"  for  ten  or  twelve  years  until  cured 
by  the  physician  Couvisart. 

The  parasite  is  contracted  by  intimate  contact  with 
a  person  who  harbors  it. 

Eradication  of  the  mite  is  easily  accomplished  by 
scrubbing  the  lesions  with  soap  and  a  soft  brush, 
followed  by  rubbing  Balsam  Peru  well  into  the  bur- 


ANIMAL  PARASITES. 


149 


rows.  Sulphur  ointment,  although  highly  recommended, 
is  not  nearly  so  efficacious. 

The  harvest-mite,  which  is  active  during 
Leptus  July  and  August,  is  a  red-colored  larvae 

AuTUMNALis.  of  a  Variety  of  TronibihidcB.     The  latter 

lives  on  grasses,  bushes,  and  grain,  and  its 
larvae  alight  on  man  as  occasion  offers.  The  red 
papules   and   wheals   which   it   produces   are   usually 


Fig.  24. — Leptus  autumnalis: 
enlarged.  (Tyson,  after  Braun.) 


Fig.  25. — Female  of 
Ixodes  ricinus,  gorged 
full,  ventral  and  dorsal 
surfaces,  f.  (After  Pa- 
genstecher.) 


situated  on  the  ankles,  but  may  also  be  found  on  other 
parts  of  the  body. 

The  wood-jack  or  wood-tick  is  a  fairly 

Ixodes       large  yellowish-brown  tick,  with  a  black 

Ricinus.      head  and  a  leathery  body.     It  is  common 

upon  grasses  and  bushes,  and  from  these 

places  gets  upon  man  and  beasts.     It  is  a  blood- suck- 


I50       INFECTIOUS  AND  PARASITIC  DISEASES. 

ing  parasite,  burying  its  head  and  sometimes  almost  its 
whole  body  in  the  integument. 

In  various  localities,  e.g.,  Africa,  and  Montana,  U.  S., 
fevers  are  described  which  are  believed  to  be  due  to 
the  bites  of  ticks  (tick-fever,  Ixodiasis);  the  evidence 
in  favor  of  such  relationship,  however,  is  contradictory. 


CHAPTER  VI. 

AVENUES  OF  EXIT  OF  INFECTIOUS  AGENTS 
AND  PARASITES  FROM  THE  BODY. 

The  source  of  every  infectious  disease  is  always 
another  infectious  disease,  that  is  to  say,  the  infectious 
agent  has  come  directly  or  indirectly  from  some  other 
person.  The  spontaneous  generation  of  disease  is  no 
longer  believed  in,  no  more  than  is  the  spontaneous 
generation  of  life  from  lifeless  matter.  It  is  true  that 
we  cannot  always  trace  the  connection  between  suc- 
cessive cases  of  the  same  disease,  but  such  instances 
are  few  in  comparison  with  the  number  in  which  the 
relationship  can  be  proven.  However,  what  has  defi- 
nitely been  determined  is  the  manner  of  exit  from  the 
body  of  micro-organisms  in  practically  all  of  the  infec- 
tious diseases  of  both  known  and  unknown  origin. 
This,  from  a  sanitary  standpoint,  is  of  surpassing 
importance,  because  it  permits  of  our  destroying  the 
infectious  agents  at  their  source  and  when  concentrated, 
and  thus  give  them  no  opportunity  to  be  scattered,  so 
to  speak,  to  the  four  winds. 

It   is   self-evident   that   the   communicability   of   a 
disease  bears  a  definite  relationship  to  the  number  of 

151 


152       INFECTIOUS  AND  PARASITIC  DISEASES. 

exits  open  to  the  causative  agents,  and  that  one  disease 
may,  therefore,  require  greater  precautions  than  another 
to  prevent  its  spread.  In  no  field  of  pubHc  utihty  does 
knowledge  confer  greater  power  than  in  sanitary 
science,  and  in  this  matter  of  the  exit  of  micro-organ- 
isms from  the  body  in  disease  we  have  the  key  to  the 
happiness  of  families,  the  prosperity  of  nations,  and  to 
victory  in  wars.  Moreover,  it  robs  disease  of  its  terrors 
by  suggesting  protective  measures  which  can  be  relied 
upon  to  be  entirely  efficient.  If  all  of  the  infectious 
agents  were  efficiently  dealt  with  upon  their  exit  from 
the  body,  the  various  diseases  to  which  they  give  rise 
would  in  time  become  traditions;  but  until  Arcadia  is 
attained  this  will  not  be  done. 

Sanitarians  in  order  to  work  in  an  enlightened  manner 
must  inform  themselves  of  both  the  direct  and  indirect 
sources  of  disease.  A  direct  source  is  a  diseased  person, 
so  that  this  study  begins  with  the  elimination  of  infec- 
tious agents  from  the  body. 

In  general  it  may  be  stated  that  microbes  leave  the 
body  in  six  ways: 

1.  In  the  expectoration  and  nasal  secretion. 

2.  In  the  stools. 

3.  In  suppurations  discharging  externally. 

4.  From  the  skin. 

5.  In  the  urine. 

6.  From  the  blood  through  the  bites  of  suctorial 
(biting)  insects. 


AVENUES  OF  EXIT  OF  INFECTIOUS  AGENTS.     153 

Perhaps  for  completeness  we  should  add  that  they 
also  make  their  exit  in  the  lachrymal  and  vaginal  secre- 
tions ;  but  since  there  is  no  specific  infection  of  the  uterus, 
and  only  a  few  of  the  conjunctiva,  these  exits  are  not  of 
sufficient  importance  to  justify  an  individual  place  in 
our  division  of  the  avenues  of  exit.  Furthermore,  the 
inflammatory  conditions  found  in  both  these  situations 
might,  with  perfect  propriety,  be  included  under  divis- 
ion three. 

The  exit  of  a  micro-organism  from  the  body  depends 
upon  the  character  and  location  of  the  disease,  namely, 
whether  it  be  local  or  general.  If  a  disease  is  localized 
in  such  a  portion  of  the  body  as  communicates  with  the 
exterior,  the  germs  make  their  exit  by  that  channel. 
Thus,  in  inflammatory  conditions  of  the  lungs,  the 
offending  microbes  are  discharged  by  way  of  the 
passages  that  lead  from  them  to  the  exterior.  Similarly, 
in  infections  of  the  uterus  the  infecting  agents  make 
their  exit  by  way  of  the  vagina.  But  if,  on  the  other 
hand,  the  disease  be  general,  that  is,  if  the  germs  are 
circulating  in  the  blood,  there  may  be  various  avenues 
of  exit,  the  urine,  the  skin,  the  sputum,  the  stools,  and 
sometimes,  through  the  bites  of  insects. 

Until  quite  recently,  many  diseases  that  we  now  know 
to  be  general  were  looked  upon  as  localized  infections, 
and  therefore  their  agents  were  supposed  to  leave  the 
body  by  a  single  channel;  but  later  researches  have  so 
modified  our  views  that  we  now  believe  there  are  very 


154       INFECTIOUS  AND  PARASITIC  DISEASES. 

few  infections  in  which  the  agents  do  not  pass  to  the 
exterior  in  a  variety  of  ways.  In  those  diseases  which 
are  both  local  and  general  we  find  the  most  numerous 
avenues  of  exit,  and  in  them  it  is  possible  for  the  infec- 
tious agent  to  leave  the  body  in  every  one  of  the  six 
ways  enumerated  above.  An  example  of  a  common 
disease  in  which  the  germs  make  their  exit  in  at  least 
five  ways,  with  a  possibility  of  six,  is  furnished  by 
typhoid  fever;  in  its  incipiency  the  bacilli  are  localized 
in  the  lower  portion  of  the  small,  and  the  beginning  of 
the  large  intestines — but  they  soon  invade  the  blood, 
and  by  the  latter  are  so  distributed  that  they  may  be 
eliminated  in  any  of  the  secretions,  in  localized  sup- 
purations, and  even  by  the  bites  of  insects. 

It  often  happens  in  the  course  of  a  disease  that  a 
micro-organism  will  make  its  exit  in  some  other  way  than 
the  channels  ordinarily  followed.  This  occurs  princi- 
pally when  complications  arise.  Therefore,  whenever, 
in  the  course  of  an  infectious  disease,  complications  arise 
in  which  there  is  a  purulent  or  other  discharge  to  the 
exterior,  these  discharges  should  be  regarded  as  fresh 
avenues  of  exit  for  the  specific  micro-organisms. 

To  be  sure,  complications  are  often  due  to  microbes  of 
a  species  different  from  the  one  causing  the  primary 
infection;  but  in  the  absence  of  definite  information  to 
the  contrary,  it  is  a  safe  rule  to  regard  complications 
as  due  to  a  migration  to  another  part  of  the  body  of 
the  first  invader.     Thus,  when  an  otitis  media  (middle- 


AVENUES  OF  EXIT  OF  INFECTIOUS  AGENTS.     155 

ear  disease)  complicates  diphtheria,  or  follows  as  a 
sequela,  the  discharge  from  the  ear  is  quite  likely  to 
contain  diphtheria  bacilli;  and  in  the  same  way  the 
purulent  pleurisy  (empyema)  which  often  complicates 
pneumonia,  is  usually  an  extension  to  the  pleura  of  the 
same  micro-organism  which  caused  the  pneumonia. 
Failure  to  give  due  regard  to  such  considerations  may 
lead  in  certain  of  the  infectious  diseases  to  serious  con- 
sequences. Cases  in  point  are  otitis  media  following 
diphtheria  and  scarlet  fever,  the  discharges  from  the 
throat  and  ear  in  either  case  remaining  infectious  for 
weeks  after  recovery.  The  virus  of  scarlet  fever  is 
especially  tenacious  in  that  way,  and  the  records  of  the 
disease  are  full  of  instances  in  which  it  has  been  con- 
veyed by  children  with  discharging  ears  after  release 
from  quarantine. 

The  sputum  is  a  prolific  source  of  infection, 

ExPECTOR-  • 

since  always  in  the  expectoration,   to  a 

ATION.  -^      .  ^ 

lesser  extent  m  the  nasal  secretions,  are 
discharged  the  microbes  that  give  rise  to  inflammatory 
conditions  of  the  air-passages :  the  lungs,  the  bronchi  and 
trachia,  the  pharynx,  the  buccal  and  nasal  cavities. 
The  inflammations  in  question  may  be  primary  in  the 
part  affected,  or  secondary  to  an  inflammatory  process 
elsewhere;  or  they  may  be  part  of  a  general  disease. 
An  example  of  these  various  conditions  is  found  in 
pneumonia.  Pneumonia  may  occur  as  an  independent 
infection;  it  may  be  secondary  to  an  inflammatory 


156       INFECTIOUS  AND  PARASITIC  DISEASES. 

process  elsewhere,  e.g.,  abscess  of  liver;  or  it  may  be 
part  of  a  general  infection,  such  as  typhoid  fever. 

In  either  the  sputum  or  nasal  secretions,  or  both,  there- 
fore, are  always  found  the  infectious  agents  of  diphtheria, 
influenza,  scarlet  fever,  whooping-cough,  mumps,  rabies 
(hydrophobia),  pneumonia,  tonsillitis,  bronchitis,  pulmo- 
nary tuberculosis  (consumption),  tubercular  laryngitis, 
cerebro-spinal  fever  (secretion  from  nose  ?) ,  measles,  acute 
glanders  (farcy),  actinomycosis,  small-pox,  leprosy  (when 
lesions  are  in  nose),  aphthous  fever  (foot  and  mouth  dis- 
ease,) echinococcus  disease  of  the  lungs,  S3^hilis  (primarily 
in  mouth),  and  typhus  fever.  Parasites — eggs  of  Para- 
gonimus  {Distoma)  Westermanii,  in  parasitic  haemoptysis. 

In  the  same  secretions,  but  only  when  the  respiratory 
passages  are  also  involved  in  the  disease,  are  found  the 
microbes  of  typhoid  fever,  anthrax,  bubonic  plague, 
actinomycosis,  amoebic  dysentery  (in  perforation  of 
abscess  of  liver  into  lung),  syphilis  (secondary),  tuber- 
culosis, leprosy,  glandular  fever  (?),  gonorrhoeal  stomat- 
itis (child  infected  during  parturition).  In  the  vom- 
itus,  it  is  always  to  be  remembered,  such  organisms  as 
cause  intestinal  diseases,  or  intestinal  parasites  and  their 
eggs,  may  be  ejected.  Thus  cholera  spirilla  have  been 
found  in  vomited  matter,  as  well  as  the  eggs  and  even 
segments  of  tape- worm. 

As  an  avenue  of  exit  for  micro-organisms 

Feces.        the  stools  rank  with  the  sputum  in  impor- 
tance, if  they  do  not  surpass  it.     Besides 


AVENUES  OF  EXIT  OF  INFECTIOUS  AGENTS.     157 

the  fact  that  there  are  as  many  infectious  processes 
locahzed  in  the  intestinal  tract  as  in  the  air-passages,  in 
all  of  which  the  microbes  are  eliminated  in  the  stools, 
the  germs  of  every  general  disease  find  their  way  into 
the  same  passage  by  way  of  the  bile.  Furthermore, 
a  host  of  animal  parasites  are  found  sporadically  in  the 
intestinal  tract  from  which  they  or  their  eggs  escape 
by  the  natural  passages.  With  one  exception,  i.e.,  in 
consumption,  the  sputum  is  chiefly  dangerous  to  those 
immediately  surrounding  the  patient;  and  even  in  this 
disease  the  infection  is  mostly  limited  to  dwellings, 
factories,  and  offices.  The  feces,  on  the  contrary,  are 
the  source  of  certain  wide-spread  infections  at  great 
distances  from  the  patient.  This  happens  because  the 
micro-organisms  causing  these  diseases  are  capable  of 
growth  outside  the  body,  particularly  in  water,  and 
because  they  are  such  as  must  be  taken  into  the  alimen- 
tary canal  to  produce  their  effects. 

In  the  matter  of  disposal  of  sewage  we  are  still  bar- 
barians, if  not  criminals ;  and  the  diffidence  with  which 
the  public  views  the  pollution  of  its  water-supply  by 
alvine  discharges  is  a  shame  to  our  much  vaunted 
civilization.  In  fact,  it  is  little  short  of  miraculous  that 
a  stop  has  not  been  put  to  it  long  ago,  when  one  con- 
siders the  wide  publicity  given  to  the  actual  and  possible 
dangers  of  such  a  filthy  and  obnoxious  practice.  But 
it  is  permitted  to  go  on,  with  the  result  that  there  is 
scarcely  a  city  or  town  that  does  not  drink  water  which 


158       INFECTIOUS  AND  PARASITIC  DISEASES. 

is  polluted  by  the  sewage  of  another  city ;  and  the  former 
places  in  turn  pour  their  disease-carrying  waste  into 
other  rivers  and  lakes  which  supply  the  drinking-water  to 
still  other  communities.  Thus  is  a  "vicious  circle"  of 
infection  maintained.  Is  it  surprising  then  that  in  this 
way  many  diseases  are  spread,  such  as  typhoid  fever, 
cholera  and  dysentery,  and  that  the  parasites  of  numer- 
ous intestinal  disorders  are  distributed  to  new  hosts  ? 

But  because  the  general  public  regards  with  indiffer- 
ence the  infliction  of  so  much  unnecessary  suffering 
and  death  is  not  a  reason  for  physicians  and  nurses 
taking  the  same  attitude.  Contrari-wise,  since  their 
chosen  fields  give  them  a  more  intimate  knowledge  of 
the  many  sources  of  disease  springing  from  ignorance 
and  folly,  and  since  they  are  thereby  more  impressed 
with  the  necessity  of  acting  in  advance  of  actual  personal 
and  public  calamity,  it  is  part  of  their  duty  to  humanity 
to  take  the  initiative  in  matters  germane  to  their  work. 
Hence  if  the  manner  of  sewer-disposal  is  a  shame  and 
blot  upon  our  civilization,  the  same  strictures  are  appli- 
cable to  physicians  and  (especially)  nurses  if  fecal 
matter  from  a  patient  is  infectious  when  disposed  of. 
Rendering  the  stools  innocuous  is  a  small  yet  imperative 
part  of  a  nurse's  daily  routine,  upon  which  the  physician 
should  insist,  and  which  the  nurse  should  conscien- 
tiously perform.  At  the  bedside,  better  than  anywhere 
else,  we  command  the  situation  in  so  far  as  the  spread  of 
disease  by  sewage  is  concerned;  and  were  disinfection 


AVENUES  OF  EXIT  OF  INFECTIOUS  AGENTS.     159 

here  always  practised,  we  would  be  going  a  long  way 
towards  balancing  the  harm  that  comes  from  the  homi- 
cidal practice  of  polluting  our  water-supplies  with  every 
conceivable  filth.  Viewed  from  this  standpoint,  there- 
fore, the  stools  assume  in  disease  an  importance  impos- 
sible to  measure. 

To  disinfect  the  feces  in  every  disease  would  be  a 
waste  of  time  and  money,  besides  being  unscientific; 
hence  the  reason  for  knowing  those  diseases  in  which 
it  is  called  for.  The  germs  which  cause  the  following 
diseases  are  always  passed  in  the  stools :  Typhoid  fever, 
Asiatic  cholera,  dysentery  (both  amoebic  and  bacillary), 
tuberculosis  (when  the  bowel  is  affected,  or  the  germs 
are  swallowed  by  the  consumptive),  bubonic  plague, 
cholera  infantum,  and  anthrax;  in  small-pox,  measles, 
scarlet  fever,  and  chicken-pox,  although  the  etiological 
factors  are  not  known,  there  is  no  doubt  that  they  are 
expelled  in  the  feces. 

The  parasites,  and  the  eggs  of  parasites,  found  in  the 
stools  are:  Eggs  and  segments  of  various  tape-worms, 
eggs  of  round- worms  {Ascaris  lumbricoides),  eggs  and 
worm  of  pin- worm  (seat  worm,  Oxyuris  vermicularis)^ 
eggs  and  worms  of  uncinaria  (in  hook-worm  disease, 
Uncinariasis),  worms  of  Strongyloides  Intestinalis 
(Endemic  diarrhoea  of  hot  countries),  eggs  of  trico- 
cephalus  dispar,  ova  in  HepaHca  Distomiasis,  ova  in 
Hcemic  Distomiasis  (Btlharziosis,  Egyptian  haematuria), 
larvae  of  common  house-fly. 


i6o       INFECTIOUS  AND  PARASITIC  DISEASES. 

The  urine  is  a  frequent  avenue  of  exit  for 
Urine.        bacteria.   They  are  found  in  it  in  practically 

all  diseases  in  which  bacteria  are  circulating 
in  the  blood  (bacteriaemia,  septicaemia),  and  also  in 
infections  of  the  genito-urinary  organs  generally.  In 
all  the  eruptive  fevers  of  known  or  unknown  origin,  the 
urine  should  be  regarded  as  infectious.  With  reference 
to  this  secretion  the  profession  learned  a  valuable 
lesson  in  the  case  of  typhoid  fever;  for  a  long  time  the 
urine  in  this  disease  was  entirely  disregarded  as  a  source 
of  infection,  yet  the  last  few  years  have  taught  us  that 
as  an  avenue  of  exit  for  the  typhoid  bacilli,  it  is  infinitely 
more  dangerous  than  the  stools.  In  the  stools,  the 
putrefactive  bacteria  which  are  always  present,  are  far 
more  vigorous  than  the  typhoid  bacilli,  so  that  if  typhoid 
stools  are  allowed  to  stand  a  day  or  two,  the  typhoid 
bacilli  disappear.  After  recovery  the  bacilli  are  not 
found  in  the  stools  unless  the  biliary  passages  are 
infected.  The  urine,  on  the  other  hand,  during  the 
whole  course  of  the  fever,  constantlycontains  the  specific 
bacilli,  often  in  such  numbers  as  to  make  it  cloudy 
(bacilluria) ;  and  what  is  far  more  important,  the  bacilli 
may  be  present  for  months  and  years  after  recovery 
unless  means  are  taken  to  eradicate  them.  In  view  of 
the  latter  fact  it  is  a  routine  practice  in  many  hospitals  to 
give  during  convalescence  from  fifteen  to  twenty  grains 
of  urotropin  daily,  or  to  wash  out  the  bladder  once  a 
day,  for  several  days  after  the  temperature  has  reached 


AVENUES  OF  EXIT  OF  INFECTIOUS  AGENTS.     i6i 

the  normal,  with  a  solution  of  bichloride  of  mercury 
(1-20,000). 

The  urine  contains  the  infectious  agents  in  the  follow- 
ing general  diseases :  Tuberculosis  (also  consumption  ?), 
pneumonia,  typhoid  fever,  anthrax,  bubonic  plague, 
influenza,  malta  fever,  and  in  all  other  bacteri^mias  or 
septicaemias  which  are  usually  classed  as  blood-poison- 
ing and  are  due  to  the  streptococcus  of  erysipelas 
(streptococcus  pyogenes),  or  to  the  common  bacterium 
of  suppuration  (staphylococcus  pyogenes  aureus). 

In    local    disease    of    the    genito-urinary 

In  Urine     organs  the  specific  micro-organisms  of  the 

IN  Local     following  infections  are  found :  Gonorrhoea, 

Diseases,    tuberculosis,    syphilis    (when    chancer    or 

secondary  lesion  is  in  the  urethra),  in  all 

infectious  diseases  of  the  kidneys,  bladder,  etc. 

Parasites       Eggs  of  parasites  in  Hcemic  Distomiasis 

AND  Eggs  of    {Biharziosis,    Egyptian   haematuria),  em- 

Parasites       bryos  in  hasmatochyluria  (associated  with 

IN  Urine.        filariasis). 

The  skin  gives  off  freely  in  scaling  the 
Skin.  infectious  elements  of  many  general  dis- 
eases, among  which  are  chiefly  the  agents 
of  the  eruptive  fevers,  such  as  scarlet  fever,  small-pox, 
measles,  chicken-pox,  erysipelas,  typhus  fever,  rubella, 
cerebro-spinal  fever  (?),  and  syphilis  (secondary).  In 
typhoid  fever,  typhoid  bacilli  have  been  found  repeatedly 
in  the  rose  spots. 


i62        INFECTIOUS  AND  PARASITIC  DISEASES. 

In  local  affections  of  the  skin,  the  agents 
Local  in    the    following   diseases    are    cast    off: 

Diseases  Cutaneous  actinomycosis,  blastomycetes, 
OF  THE  Skin,  ring-worm  of  various  parts  of  the  body, 

tinea  sycosis  (barber's  itch),  favus,  tinea 
versicolor,  impetigo  contagiosa,  furunculi  (boils),  malig- 
nant pustule  (local  anthrax),  erysipelas,  pinto  (spotted 
sickness),  mycetoma  (Madura  foot),  lupus  vulgaris 
(cutaneous  tuberculosis),  syphilis,  leprosy,  yaws,  glan- 
ders (farcy),  etc. 

Animal  parasites  are  found  in  these  affec- 
Parasites  tions  of  the  skin:  Scabies,  pediculosis 
OF  Skin.  (pubis,  capitis,  vestimentorum),  Craw-craw, 

and  Guinea-worm  disease  (Dracunculus 
medinensis).  The  larvae  of  the  common  house-fly  are 
sometimes  found  in  wounds,  and  the  grubs  or  larvae  of 
special  flies  (bot-fly,  gad-fly,  etc.),  in  tropical  and  sub- 
tropical countries,  quite  frequently  take  up  their  abode 
beneath  the  skin. 

The  blood  as  an  avenue  of  exit  for  infec- 
Blood.       tious  agents  was  a  sterile  field  for  research 

until  the  relationship  of  a  biting  insect  to  a 
disease  was  established  by  the  discovery,  in  1893,  by 
Theobald  Smith,  that  a  tick  is  the  intermediate  host  for 
the  micro-organism  of  Texas  cattle  fever.  Long  before 
this  discovery  physicians  had  suspected  that  mosquitoes 
played  a  role  in  both  malaria  and  yellow  fever — but 
the  proofs  were  lacking  in  both  diseases.     These  have 


AVENUES  OF  EXIT  OF  INFECTIOUS  AGENTS.     163 

now  been  supplied,  with  additional  evidence  that  another 
disease,  filariasis,  is  conveyed  in  the  same  way.  It  is 
quite  probable  that  many  communicable  diseases  whose 
infectious  agents  are  still  a  mystery  may  be  transmitted 
by  suctorial  insects — at  least  this  is  suspected — but 
these  are  facts  for  future  investigations  to  disclose. 

It  is  often  as  important  to  know  the  manner  of  trans- 
mission of  a  disease  as  its  cause,  because  this  may  supply 
the  only  data  for  combating  it.  Just  this  much  is  the 
sum  of  our  knowledge  of  yellow  fever,  yet  that  it  may 
be  controlled  has  been  conclusively  proven  by  Major 
Gorgas  of  the  U.  S.  Army,  in  Havana,  Cuba,  and  by 
officers  of  the  U.  S.  Public  Health  and  Marine-Hospital 
Service,  in  Louisiana  last  year  (1905).  The  yellow 
fever  commission  appointed  by  the  Surgeon- General 
of  the  U.  S.  Army,  the  commission  to  which  we  owe 
our  knowledge  of  the  transmission  of  yellow  fever  by 
mosquitoes,  after  it  had  made  the  latter  discovery,  was 
able  also  to  eliminate  every  other  avenue  of  exit  for  the 
causative  agent  except  the  blood,  and  thus  made  clear 
the  futility  of  attempting  to  circumscribe  the  disease  by 
disinfection  of  secretions,  fomites,  etc.  It  further 
showed  that  extermination  of  mosquitoes  offers  the  only 
solution  of  this  sanitary  problem,  because  in  no  other 
way  can  this  unknown  virus  get  out  of  one  patient's 
body  and  into  another.  Therefore,  when  we  say  a 
micro-organism  makes  its  exit  in  the  blood,  it  is  under- 
stood that  this  is  accomplished  through  the  bite  of  an 


i64       INFECTIOUS  AND  PARASITIC  DISEASES. 

insect.  From  the  blood,  through  the  bites  of  suctorial 
insects,  the  microbes  of  malaria,  yellow  fever,  filariasis 
and  trypanosomiasis  (sleeping-sickness),  always  make 
their  exit.  Dengue  is  also  believed  to  be  conveyed  in 
this  way.  In  typhus  fever,  bubonic  plague,  typhoid 
fever,  and  the  bacteriaemias  generally,  there  is  always 
the  possibility  of  microbes  being  extracted  when  a 
patient  is  bitten.  Bed-bugs  may  suck  out  the  spirilla 
in  relapsing  fever,  to  prove  which  the  disease  has  been 
produced  in  a  monkey  by  inoculating  it  with  blood 
obtained  from  a  bug  that  had  bitten  another  monkey 
suffering  from  this  infection. 

In  suppurative  processes  the  micro-organ- 

SuppuRA-  jgj^g  causing  the  trouble  are  always  ex- 
pelled in  the  escaping  material.  In  the  fol- 
lowing specific  infections  the  offending  microbe  is  dis- 
charged in  the  pus:  Erysipelas,  anthrax  (malignant 
pustule),  glanders  (farcy),  malignant  oedema,  gonor- 
rhoea (ophthalmia  neonatorum,  urethral  and  uterine 
gonorrhoea),  diphtheria,  syphilis,  tuberculosis,  tetanus 
(lock-jaw),  leprosy,  actinomycosis,  amoebic  abscess, 
trachoma  (Egyptian  ophthalmia),  catarrhal  conjunc- 
tivitis, blastomycetis,  etc. 

Non-specific  suppurations  are  caused  by  a  variety 
of  microbes,  among  which  the  streptococcus  pyogenes, 
and  the  several  varieties  of  the  staphylococcus,  are 
principally  concerned;  less  frequently  are  found  the 
bacillus  coli  communis  and  the  micrococcus  tetragenus. 


AVENUES  OF  EXIT  OF  INFECTIOUS  AGENTS.     165 

Boils,  carbuncles,  many  pure  and  mixed  cutaneous 
suppurations,  and  suppurations  found  elsewhere  in 
the  body,  also  come  under  this  head.  The  guinea- 
worm  discharges  its  embryos  and  also  makes  its  own 
exit  in  a  cutaneous  suppuration  which  it  excites. 

In  puerperal  fever  (child-bed  fever),  the  infecting 
micro-organism  is  discharged  in  the  vaginal  secretion, 
or  from  such  other  suppurating  foci  as  may  be  estab- 
lished during  the  illness.  In  scarlet  fever,  small-pox, 
typhoid  fever,  etc.,  when  suppurations  ensue,  the  dis- 
charges contain  the  infectious  agents. 

The  principal  communicable  specific  infectious  dis- 
eases of  the  eye  in  which  the  specific  micro-organisms 
are  discharged  in  pus,  are  gonorrhoeal  ophthalmia, 
catarrhal  conjunctivitis,  diphtheritic  conjunctivitis, 
and  trachoma  (Egyptian  ophthalmia). 


CHAPTER  VII. 

PORTALS  OF  ENTRY  OF  INFECTIOUS  AGENTS 
AND  OF  PARASITES  INTO  THE  BODY. 

Microbes  must  observe  a  more  regular  manner  of 
entering  the  body  than  leaving  it,  if  they  would  produce 
disease.  This  is  due  to  the  fact  that  tissues  differ  in 
vulnerability  to  their  attack,  being  favorable  to  the 
growth  of  some  germs,  and  unfavorable  to  others.  The 
same  variation  in  susceptibility  is  noticed  in  the  various 
organs  of  the  body,  and  in  different  localities  even 
where  the  tissues  are  not  perceptibly  dissimilar.  From 
this  is  would  appear  that  bacteria  are  preferential  in 
their  action,  a  conception  that  is  quite  generally  believed. 
However,  while  admitting  that  infectious  agents  have  a 
selective  action,  we  must  not  overlook  the  part  taken  by 
the  body  in  limiting  microbic  action  through  its  secre- 
tions and  anatomical  peculiarities.  Thus  it  is  well 
established  that  the  liver,  through  its  secretions,  has 
astonishing  germicidal  powers,  and  that  to  this  influence 
we  undoubtedly  owe  immunity  from  many  infections. 
Again,  the  comparative  freedom  of  the  eye  from  infec- 
tion is  largely  a  result  of  winking,  by  which  act  mechan- 
ical removal  of  bacteria  is  accomplished.     As  a  conse- 

i66 


PORTALS  OF  ENTRY  OF  INFECTIOUS  AGENTS.     167 

quence  of  the  peculiarities  just  explained,  a  microbe 
cannot  do  harm  if  it  enters  the  body  unless  it  finds 
lodgment  in  a  situation  favorable  to  its  growth.  In 
other  words,  the  microbe  and  opportunity  must  meet 
for  the  production  of  disease.  Example:  The  tetanus 
(lock-jaw)  bacillus  is  fatal  if  it  enters  a  wound  however 
trivial,  yet  it  may  be  swallowed  (indeed,  often  is) 
with  impunity. 

The  portals  of  entry  of  infectious  agents  and  parasites 
into  the  body  may  be  included  under  the  following 
heads : 

1.  Through  wounds  of  skin  and  mucous  membranes. 

2.  By  the  mouth  or  nose,  through  air. 

3.  By  mouth,  through  food  and  water. 

4.  By  genito-urinary  tract. 

5.  By  placenta  (congenital  infection). 

6.  Cryptogenic  (unknown). 

The  immediately  accessible  portions  of  the  body  to 
infectious  agents  are  either  covered  with  skin  or  mucous 
membranes,  so  that  in  the  production  of  disease,  one 
of  those  surfaces  must  be  penetrated.* 

If  an  infection  can  be  contracted  either  through 
wounds  of  the  skin  or  mucous  membranes,  it  is  said  to 
be  inoculable.     It  is  still  a  question  in  dispute  whether 

*To  make  this  generalization  clear  it  is  only  necessary  to  remind  the 
reader  that  the  air-passages  have  a  mucous  Hning  from  their  external 
openings  down  to  their  final  terminations  in  air  cells  in  the  lungs;  and 
that  the  alimentary  tract  is  lined  with  an  uninterrupted  sheet  of  mucous 
membrane  from  inlet  to  outlet. 


i68       INFECTIOUS  AND  PARASITIC  DISEASES. 

in  this  sense  all  infectious  diseases  are  not  inoculable, 
that  is  to  say,  whether  the  entrance  of  the  agent  does  not 
depend  upon  some  defect  created  in  the  integument  or 
mucous  membrane  by  another  cause.  Neither  the 
nature  of  the  infectious  agent  nor  the  region  of  the  body 
which  is  the  primary  site  of  the  disease  enter  into  the 
discussion;  nor  is  it  disputed  that  penetration  must 
occur;  the  question  is,  how  does  it  happen,  whether 
through  the  action  of  the  bacteria  themselves,  or  through 
the  agency  of  another  cause?  If  an  accessory  cause 
paves  the  way  in  all  infections  by  interrupting  the  con- 
tinuity of  a  surface,  then  all  infectious  diseases  are  inoc- 
ulable. This  latter  belief,  it  will  be  recalled,  is  in 
entire  accord  with  views  previously  expressed  in  the 
chapter  on  "The  Phenomena  of  Infection,"  particularly 
in  that  portion  which  treats  of  the  part  the  body  plays 
in  its  production. 

The  lesions  of  entrance  in  some  diseases  are  more 
palpable  than  they  are  in  others,  and  in  others  again, 
they  can  never  be  found;  yet  that  this  latter  fact  is  not 
a  safe  argument  to  use  against  the  inoculability  of  a 
disease  will  be  seen  from  a  few  illustrations.  Take, 
for  example,  such  a  disease  as  yellow  fever.  Before 
the  epochal  work  of  the  medical  officers  of  the  U.  S. 
Army  in  Cuba,  during  1898-99,  yellow  fever  was 
regarded  as  a  highly  contagious  disease,  to  guard 
against  which  it  was  deemed  necessary  not  only  to 
subject  exposed  individuals  to  the  most  rigid  quarantine. 


PORTALS  OF  ENTRY  OF  INFECTIOUS  AGENTS.     169 

but  also  to  fumigate  clothing,  bedding,  and  even  letters, 
that  had  been  in  most  casual  contact  with  the  sick. 
The  measures  enforced  indicate  that  the  causative 
agent  was  believed  capable  of  gaining  an  entrance  into 
the  body  without  injury  to  the  skin  or  mucous  mem- 
branes. We  now  know,  however,  that  a  lesion  of  the 
skin  inflicted  by  a  mosquito  is  its  only  means  of  entrance 
(although  we  are  yet  in  the  dark  as  to  the  nature  of  the 
agent),  and  that,  therefore,  all  former  methods  of  pre- 
vention were  futile  in  so  far  as  control  of  the  disease  was 
concerned.  Into  such  gross  errors  is  it  possible  to 
fall  when  we  apply  methods  of  proven  value  in  known 
to  unknown  diseases!  Another  case  in  point:  Take 
typhoid  fever;  the  typhoid  bacillus  enters  the  body  by 
the  mouth  in  food  or  drink.  The  most  obvious  lesions 
of  the  disease  are  seen  in  ulcers  of  the  lymph  nodes 
(glands)  of  the  lower  part  of  the  small  and  the  beginning 
of  the  large  intestines.  To  affect  these  results  the 
bacilli  pass  through  the  mucous  membrane  of  the 
bowels,  where  they  can  be  seen  with  the  microscope  in 
stained  sections  after  death.  The  specific  bacilli, 
however,  do  not  stop  in  the  sub-mucosa  (sub-mucous 
tissue)  but  pass  from  here  into  the  blood,  where  active 
growth  and  toxin  formation  is  carried  on.  In  other 
words,  typhoid  fever  belongs  to  the  bacteriaemias,  a 
class  of  diseases  characterized,  as  we  have  seen,  by  the 
presence  of  bacteria  in  the  blood.  Usually  the  more 
obvious  symptoms  of  typhoid  fever  are  those  referable 


I70       INFECTIOUS  AND  PARASITIC  DISEASES. 

to  the  bowels;  but  the  intestinal  features  may  be  com- 
pletely wanting,  as  has  been  repeatedly  proven  by  post 
mortem  examinations.  Such  cases  are  usually  reported 
as  ^^ Typhoid  fever  without  intestinal  lesions."  A 
study  of  typhoid  fever,  therefore,  teaches  that,  while 
the  agents  of  a  disease  may  depend  for  entrance  into 
the  blood  upon  a  gross  or  macroscopic  lesion  of  a 
mucous  membrane,  they  also  may  enter  through  a  non- 
demonstrable  portal.  It  might  be  asked  at  this  point, 
^^why  do  not  the  bacteria  which  get  into  the  intestinal 
tract  with  food,  and  those  which  have  their  habitat  there, 
often  penetrate  the  mucosa  and  cause  disease?"  The 
answer  to  which  would  be,  they  do,  far  oftener  than  is 
generally  supposed;  in  fact  the  intestinal  tract  is  re- 
garded as  the  chief  portal  of  entry  for  many  diseases 
for  which  no  atria  can  be  found  (cryptogenic  infections). 
That  some  bacteria  can  enter  certain  tissues  and 
attack  certain  localities  more  readily  than  others  is 
admitted,  because  it  has  been  experimentally  proven. 
But  between  experiments,  no  matter  how  cunningly 
devised,  and  disease,  as  ordinarily  contracted,  there  is  a 
wide  gap.  When  an  animal  or  person  is  subjected  to 
the  germs  of  a  disease,  many  million  times  the  number 
of  bacteria  are  applied  than  are  ever  present  under 
natural  conditions.  Under  such  circumstances  mere 
contact  of  these  germs  with  the  right  mucous  surface  is 
sufficient  to  provoke  disease.  This  is  the  case,  for 
example,  with  the  diphtheria  bacillus,  accidental  infec- 


PORTALS  OF  ENTRY  OF  INFECTIOUS  AGENTS.     171 

tions  with  which  having  occurred  in  laboratories  by  a 
culture  being  unwittingly  drawn  up  into  the  mouth. 
But  under  natural  conditions  of  infection,  where  only 
casual  contact  between  a  patient  and  another  person 
takes  place,  how  can  we  believe  that  very  many  germs 
reach  the  throat  through  inhalation?  Certainly  they 
are  by  far  not  so  numerous  in  air  as  when  grown  in 
cultures!  Furthermore,  in  every  disease,  we  concede 
the  co-operation  of  contributing  or  predisposing  causes : 
enlarged  tonsils  and  adenoids  in  diphtheria;  exposure 
and  alcoholism  in  pneumonia;  indigestion,  fatigue, 
and  over-ripe  fruits,  in  cholera,  etc.  Why  ?  if  the  germs 
acting  alone  are  sufficient? 

Finally,  only  a  limited  number  of  persons  exposed 
to  an  infectious  disease  contract  it,  a  fact  which  cannot 
be  explained  in  the  case  of  local  diseases  on  grounds  of 
greater  general  predisposition.  In  diphtheria,  gonor- 
rhoea, cholera,  etc.,  might  it  not  be  because  in  those 
persons  that  we  say  are  susceptible,  the  predisposing 
causes  ultimately  resolve  themselves  into  invisible 
breaks  or  ruptures  in  the  continuity  of  mucous  sur- 
faces ? 

The  subject  of  the  inoculability  of  diseases  has  been 
thus  fully  discussed  because  of  our  classification  of  the 
portals  of  entry.  We  have  endeavored  to  show  that 
our  first  group,  "through  wounds  of  skin  or  mucous 
membranes,"  might  be  made  to  include  practically  all 
diseases  of  known  etiology.     But  such  a  division  is 


172       INFECTIOUS  AND  PARASITIC  DISEASES. 

ill-suited  to  our  purpose,  which  is  to  direct  attention 
to  the  more  obvious  atria,  and  also  to  those  portions  of 
the  body  as  are  most  likely  to  be  the  primary  or  initial 
seat  of  the  various  infections.  Syphilis  well  illustrates 
our  aim.  Syphilis  is  a  typical  inoculable  disease,  a 
break  in  the  integument  or  a  mucous  surface  being 
required  for  entrance  of  the  virus.  But  if  we  only 
treated  of  its  portals  of  entry  under  lesions  of  the  skin 
and  mucous  membranes,  data  of  the  highest  importance 
would  not  be  included.  Nothing,  for  example,  would 
be  said  of  the  fact  that  the  initial  infection  is  usually 
found  upon  the  genitalia,  not  that  the  infection  is 
hereditary.  Hence,  the  reason  for  employing  a  classi- 
fication apparently  illogical. 

The  more  obvious  portals  are  those  easiest  remem- 
bered, and  the  most  practical;  and  therefore,  under  the 
inoculable  diseases  are  placed  those  which  are  either 
contracted  through  visible  lesions,  or  can  be  inoculated, 
although  under  natural  conditions  this  may  not  seem  to 
occur;*  and  under  the  other  divisions  are  grouped 
those  which  experience  has  taught  attack  one  portion 
of  the  body  rather  than  another.  Obviously  under  such 
a  classification,  a  disease  will  often  be  found  under  two 
or  more  heads. 

♦Example: — Small-pox  is  ordinarily  contracted  by  contact  of  an  un- 
vaccinated  person  with  a  patient  or  fomites.  That  it  is  directly  inocu- 
lable, the  earlier  practice  of  variolation,  introduced  into  England  by 
Lady  Mary  Worthey  Montague  in  1727,  shows. 


PORTALS  OF  ENTRY  OF  INFECTIOUS  AGENTS.     173 

The  strictly  inoculable  infectious  diseases 
Skin  and  are  tetanus  (lock-jaw),  syphilis  (acquired), 
Mucous  lupus  vulgaris  (cutaneous  tuberculosis). 
Membranes,  erysipelas,  actinomycosis  (cutaneous), 
glanders  (farcy),  leprosy  (?),  typhus  fever, 
plague,  anthrax  (malignant  pustule),  hydrophobia, 
mountain  fever  (?),  foot  and  mouth  disease,  malarial 
fever,  yellow  fever,  filariasis  (elephantiasis)  blastomy- 
cetes,  mycetoma  (Madura  foot),  small-pox,  and  soft 
chancer. 

Vegetable  parasites  are  the  cause  of  ring-worms  of 
various  parts  (tinea  tonsurans,  tinea  circinata),  barber's 
itch  (tinea  sycosis),  tinea  versicolor,  pinto  (spotted  sick- 
ness), yaws,  and  craw-craw.  Thrush  is  a  vegetable 
parasitic  affection  of  the  mucous  membrane  of  the 
tongue  and  cheeks  of  infants. 

Animal  parasites  which  gain  entrance  through  the 
skin  are  represented  by  the  embryos  of  the  uncinaria 
(parasite  of  hook-worm  disease). 

Parasitic  insects  of  the  skin  are  Sarcoptes  scabiei 
(itch-mite) ;  the  head,  body,  and  pubic  louse;  the  larva  of 
the  horse  bot-fly  (gastrophilus  equi),  which  causes 
''Creeping  Eruption;"  mosquitoes,  which  inoculate  the 
agents  of  malaria,  yellow  fever  and  filariasis,  and  prob- 
ably that  of  dengue;  and  the  fly  glossina  which  prob- 
ably inoculates  the  parasites  of  trypanosomiasis 
(sleeping-sickness) . 

The  mouth  is  a  portal  of  entry  for  infectious  agents 


174       INFECTIOUS  AND  PARASITIC  DISEASES. 

and  parasites  in  both  air  and  foods,  and  in  the  case  of 
many  diseases  both  methods  of  conveyance  are  possible. 
Yet  because  some  diseases  are  nearly  always,  or  even 
exclusively,  contracted  in  one  of  these  v^ays,  it  has 
seemed  best  to  make  a  division  of  diseases  into  those 
inspired,  and  those  taken  in  with  foods  and  water. 
For  example,  neither  Asiatic  cholera  nor  dysentery  are 
ever  air-borne;  nor  is  pneumonia  contracted  in  either 
food  or  drink;  yet  in  diphtheria,  scarlet  fever,  small-pox, 
etc.,  both  air  and  foods  are  fruitful  sources  of  infection. 
The  air,  however,  as  a  source  of  contagion,  has  been 
much  exaggerated  in  the  past,  particularly  where  trans- 
mission of  a  disease  over  great  distances  has  been  laid 
at  its  door.  With  the  exception  of  diseases  conveyed 
by  insects,  such  as  mosquitoes,  which  may  be  blown 
by  winds,  there  is  really  no  readily  communicable 
disease  which  is  dangerous  to  others  in  the  open  air 
at  a  few  yards  distance.  The  fear  that  many  persons 
have  of  passing  a  house  where  a  contagious  disease 
exists  is  without  foundation.  Carelessness  within  the 
house  may  be  responsible  for  every  room  being  danger- 
ous— but  that  does  not  affect  the  air  outside.  When 
carefully  investigated  the  so-called  air-borne  infections 
are  discovered  to  have  been  carried  by  a  third 
person,  or  by  some  article  used  and  soiled  in  the  sick- 
room. Usually  it  is  the  former.  The  truth  is  graphic- 
ally presented  by  Dr.  Rosenau  who  quotes  Dr. 
J.  H.  White,  ''that  infectious  diseases  are  more  often 


PORTALS  OF  ENTRY  OF  INFECTIOUS  AGENTS.     175 

conveyed  from  place  to  place  in  two  shoes  than  in  any 
other  way."  Therefore,  air-borne,  as  applied  to  a 
disease,  rather  emphasizes  the  fact  that  the  contagion 
enters  by  way  of  the  respiratory  passages,  than  that  it 
is  widely  diffused  in  air. 

By  the  mouth  and  nose  through  air  may 
enter  the  infectious  agents  in  small-pox, 

AND   Nose  ...  ^  ^  r 

THROUGH  chicken-pox,  measles,  scarlet  fever,  mumps. 
Air.  whooping-cough,  pneumonia,  tuberculosis, 

diphtheria,  plague,  anthrax,  epidemic  cere- 
bro-spinal  meningitis  (?),  rubella  and  influenza. 

A  large  number  of  the  infectious  and  para- 
MouTH  gj|.j^   diseases   are   contracted   exclusively 

P  by  the  pathogenic  agents  entering  the  body 

Water.  ^^  foods  and  water.     This  method  of  infec- 

tion is  also  by  no  means  unusual  in  certain 
diseases  for  which  the  respiratory  passages  are  the  ordi- 
nary portals  of  entry.  Foods  and  water,  as  a  rule,  offer 
excellent  pabula  for  infectious  agents  and  parasites, 
and  are  therefore  quite  frequently  the  means  by  which 
diseases  are  spread.  The  pollution  of  drinking-water  by 
sewage,  and  the  harm  arising  therefrom,  has  already 
been  considered.  Foods  in  relation  to  disease,  however, 
requires  some  further  elucidation;  and  while  it  is  not 
our  aim  to  take  up  all  foods  which  serve  as  vehicles  for 
infectious  and  parasitic  agents,  the  manner  of  con- 
tamination of  some  of  those  consumed  daily  will  serve 
to  illustrate,  in  a  general  way,  how  these  are  a  source  of 


176       INFECTIOUS  AND  PARASITIC  DISEASES. 

disease.  Furthermore,  the  movement  of  food-stuffs 
from  one  part  of  a  country  to  another,  or  from  one 
country  to  another,  will  be  sufficiently  dealt  with  to 
show  the  possibilities  of  diseases  being  literally  picked 
up,  carried  hundreds  of  miles,  and  transplanted  in 
regions  where  they  previously  did  not  exist. 

Mention  has  been  made  of  the  manner  in  which 
typhoid  fever,  cholera,  dysentery,  etc.,  are  contracted 
from  drinking  polluted  water.  Polluted  water,  how- 
ever, although  it  may  not  be  used  for  drinking  purposes, 
may  nevertheless  be  a  source  of  danger  from  certain 
foods  which  grow  in  it  and  are  consumed  raw.  This 
danger  has  been  realized  a  number  of  times  in  the  case 
of  oysters  and  clams;  and  while  water-cress  has  not 
yet  been  definitely  incriminated,  there  is  no  reason 
why  it  may  not  be  a  menace  to  health  in  the  same 
way. 

Fruits  and  vegetables  are  sometimes  polluted  by  the 
fertilizer,  especially  where  human  excrement  is  used  to 
enrich  the  soil.  In  the  United  States  this  practice  is 
not  so  common  as  in  certain  European  countries,  nor 
in  the  latter  countries  as  in  China,  where  it  is  the  rule. 
But  the  number  of  Chinese  truck-farmers  in  the 
United  States  and  Cuba  is  not  small,  and  steps  should 
be  taken  to  illegalize  the  use  of  human  excrement  for 
fertilizer  unless  it  has  been  made  innocuous  by  various 
approved  methods.  Only  a  few  years  ago,  during  the 
American  occupation  of  Cuba,  several  Army  Surgeons 


PORTALS  OF  ENTRY  OF  INFECTIOUS  AGENTS.     177 

made  the  filthy  farming  customs  of  the  Chinese  the  sub- 
ject of  special  reports.  It  is  scarcely  necessary  to 
mention  the  way  human  excrement  used  as  fertilizer  is 
dangerous,  as  it  differs  in  no  respect  from  fecal  pollution 
of  water;  nor  that  the  chief  danger  comes  from  vege- 
tables, berries,  and  salads  which  are  eaten  raw. 

Pollution  of  berries,  etc.,  may  also  come  from  the 
persons  employed  in  gathering  them.  The  people 
engaged  in  this  kind  of  labor,  while  they  are  on  the  one 
hand  drawn  from  the  most  densely  ignorant  and  un 
cleanest  of  foreigners,  are  on  the  other  denied  for  weeks 
the  most  primitive  accessories  of  civilization.  Whole 
families,  men,  women,  and  children,  in  the  early  spring 
begin  a  migration  which  starts  where  the  season  opens 
soonest,  and  ends  in  the  fall  where  it  closes  last.  Dur- 
ing this,  the  warmest  part  of  the  year,  they  live  in  the 
fields  in  tents  or  covered  wagons,  working  from  sunrise 
to  sunset  with  only  such  conveniences  as  their  tempo- 
rary abiding-places  afford.  They  ask  very  little  in  the 
way  of  comforts  and  get  less.  A  bath  to  most  of  them 
is  ordinarily  obnoxious.  From  their  bunks  day  after 
day  they  go  to  their  work  in  the  dawning  morning, 
unwashed  and  uncombed,  to  return  at  night  to  sleep, 
too  exhausted  to  make  an  effort  to  be  clean.  Relief 
from  physiological  emergencies  is  sought  where  they 
work,  and  quickly  too — for  the  remuneration  is  *^so 
much  the  measure."  Sickness  often  prevails  in  these 
camps,   typhoid  fever,   small-pox,   scarlet  fever,   etc.. 


178       INFECTIOUS  AND  PARASITIC  DISEASES. 

and  many  workers  harbor  intestinal  parasites.  Need 
more  be  said  of  the  probability  of  disease  being  served 
at  our  tables  with  fresh  fruits  and  vegetables?  Could 
the  egg  of  a  tape- worm  find  a  more  toothsome  vehicle  ? 
And  yet  there  are  those  who  insist  on  eating  berries 
unwashed  because  they  lose  a  little  flavor  in  the  wash- 
ing! 

Some  articles  of  food  are  more  favorable  to  the  growth 
of  bacteria  than  others.  Milk  is  the  best.  This  is 
unfortunate,  because,  besides  being  a  natural  food  for 
children  and  the  greatest  boon  in  sickness,  it  is  next 
to  bread  the  most-used  article  of  diet.  Because  it 
furnishes  such  an  excellent  pabulum  for  bacteria,  it  is  a 
frequent  vehicle  by  which  they  are  carried.  Sickness 
in  a  milker,  or  in  a  dairyman's  family,  or  the  washing 
of  milk-cans  in  polluted  water,  has  time  and  again 
caused  epidemics  of  scarlet  fever,  diphtheria,  and 
typhoid  fever,  a  fact  which  calls  for  the  enactment  of 
rigid  laws  regulating  the  production,  handling,  and 
sale  of  milk,  and  severe  penalties  for  infractions  of  this 
law. 

For  a  long  time  it  has  been  the  custom,  when  a  few 
cases  of  typhoid  fever  occur  in  a  community,  to  imme- 
diately impugn  the  character  of  the  water-supply. 
This  attitude  of  mind  is  a  legacy  of  the  time  when  pol- 
luted water  was  believed  to  be  the  only  source  of  this 
infection.  Where  large  numbers  of  cases  occur,  and 
especially  if  they  are  not  limited  to  one  neighborhood, 


PORTALS  OF  ENTRY  OF  INFECTIOUS  AGENTS.     179 

it  is  a  wise  precaution  to  suspect  the  drinking-water. 
But  where  cases  are  reported  sporadically,  especially 
in  communities  which  have  a  municipal  water  system, 
it  is  more  logical  to  seek  the  source  elsewhere.  The 
modern  method  of  food  distribution  is  a  marvelous 
development,  that  is  comparable  to  other  inventions  of 
the  19th  Century.  Through  it  perishable  articles  are 
not  only  distributed  from  one  point  where  the  supply 
exceeds  the  demand  to  others  where  they  are  needed; 
but  they  are  also  held,  in  the  case  of  certain  foods,  a 
year  or  more — if  the  supply  is  too  abundant.  Nor  is 
the  distribution  of  such  things  limited  to  the  farther- 
most boundaries  of  one  country,  but  they  are  also 
shipped  from  one  country  to  another  across  the  widest 
seas.  All  this  has  come  about  through  the  expansion 
of  the  cold  storage  business,  and  the  use  of  refrigerator 
cars,  and  cold  storage  plants  on  steam-ships.  There 
is  a  large  and  ever  increasing  demand  for  various  perish- 
able articles  of  food  out  of  season,  so  that  there  is  a 
constant  movement  of  supplies  from  one  region  to 
another.  Furthermore,  this  demand  has  stimulated 
the  speculative  zeal  of  those  engaged  in  the  cold  storage 
business,  with  the  result  that  ''in  season"  enormous 
storing  of  perishable  foods  is  conducted.  So  great  at 
these  times  is  the  demand  for  these  commodities  for 
storage,  and  for  shipment  to  other  parts  of  the  country, 
that  in  many  localities  where  they  are  grown  it  is  im- 
possible to  purchase  in  the  local  market  either  fresh 


i8o       INFECTIOUS  AND  PARASITIC  DISEASES. 

fowl,  eggs,  milk,  butter,  fruits  and  game.  Hence  it  is 
probably  true,  although  we  haven't^the  support  of  figures 
for  the  assertion,  that  more  of  the  above  mentioned 
foods  are  eaten  out  of  season  than  in. 

Our  reason  for  dwelling  upon  this  phase  of  modern 
economic  life  is  to  draw  attention  to  the  probability 
of  communicable  diseases  being  carried  with  foods 
from  points  widely  separated,  and  the  difficulty  of 
tracing  those  so  carried  to  their  source.  Refrigeration 
does  not  necessarily  kill  infectious  agents  and  animal 
parasites,  indeed,  we  have  already  called  attention  to 
the  dangers  of  ice  in  relation  to  typhoid  fever  and  cholera; 
so  that  through  this  system  some  contaminated  article 
such  as  cream,  may  first  be  shipped  five  hundred  miles 
to  a  creamery,  churned  into  butter  there,  held  in 
storage  a  few  months,  and  finally  be  shipped  another 
thousand  miles,  or  across  the  ocean  to  Europe.  The 
possible  contamination  of  fruits,  berries,  and  vegetables 
by  those  that  pluck  them  has  been  considered  a  few 
lines  above ;  in  the  refrigerator  car,  therefore,  we  see  a 
way  by  which  iinfectious  or  parasitic  agents  contamina- 
ting such  products  may  be  transported. 

By  the  mouth  through  foods  and  water,  are  taken  in 
the  agents  of  typhoid  fever,  Asiatic  cholera,  small-pox, 
measles,  scarlet  fever,  tuberculosis,  diphtheria,  plague, 
anthrax,  syphilis,  amoebic  and  bacillary  dysentery, 
actinomycosis,  milk  sickness,  and  aphthous  fever  (foot 
and  mouth  disease). 


PORTALS  OF  ENTRY  OF  INFECTIOUS  AGENTS.     i8i 

The  following  eggs,  embryos,  or  parasites 
Parasites  are  taken  into  the  body  with  foods  or  water : 
OR  Eggs  of  Eggs  of  beef  tape-worm  (T^ma  saginata); 
Parasites,      eggs  and  larvae  of  pork  tape-worm  {tcBnia 

solium);  eggs  of  Taenia  echinococcus  (dog 
tape- worm),  water;  eggs  of  round  worm  (ascaris  lumbri- 
coides),  water;  eggs  of  pin- worm  (Seat-worm,  Oxyuris 
vermicularis)^  water;  larvas  of  Guinea- worm  {Dracun- 
culus  medinensis),  water;  larvae  of  trichinae  (Trichinia- 
sis),  pork;  larvae  of  Uncinaria  (hook-worm  disease), 
water  and  soil;  worm  of  Strongyloides  Intestinalis 
(endemic  diarrhoea  of  hot  countries),  water  (?);  eggs 
of  tricocephalus  dispar;  eggs  of  parasite  causing  Bilhar- 
ziosis  (Egyptian  haematuria),  (?);  larvae  of  common 
house-fly. 

The  commonest  infectious  diseases  of  the 
Genito-  genito-urinary  organs  are  the  so-called 
urinary  '' venereal  diseases,"  gonorrhoea  and  syph- 
Tract.        iiis.     Both  of  these   infections,   however, 

may  be  found  elsewhere  upon  the  body  in 
persons  innocent  of  wrong-doing.  In  such  cases  the 
name  of  the  disease  is  qualified  by  the  word  insontium 
written  after  it.  In  the  female  the  vulva,  vagina, 
urethra,  and  cervix  of  the  uterus,  are  often  the  seat  of 
gonorrhoea  and  syphilis,  less  often,  of  tuberculosis. 
Following  abortion,  or  delivery  at  term,  the  uterus  is 
frequently  infected  with  the  streptococcus  of  erysipelas, 
the  colon  bacillus  (from  feces),  and  the  common  mi- 


i82       INFECTIOUS  AND  PARASITIC  DISEASES. 

crobes  which  cause  suppuration.     Occasionally  the  ex- 
ternal genitals  are  the  seat  of  diphtheria. 

In  the  male,  syphihtic  and  gonorrhoeal  lesions  of  the 
outside  of  the  penis  are  common.  The  interior  of  the 
urethra  is  seldom  affected  by  any  other  disease  besides 
gonorrhoea.  However,  chancer  (syphilis)  of  the  inside 
of  the  urethra  is  sometimes  encountered. 

The  bladder  in  both  sexes  is  frequently  the  seat  of 
inflammations  (cystitis),  the  infection  very  often  being 
carried  into  the  bladder  by  catheterization.  Besides 
getting  into  the  bladder  by  way  of  the  urethra,  however, 
the  infection  may  come  from  the  blood  by  way  of  the 
kidneys.  Tuberculosis  of  the  bladder,  a  not  uncommon 
infection,  usually  arises  in  this  way. 
Animal  The  round  worm  has  been  found  in  the 

Parasites.      vagina. 

Only  one  congenital  disease  occurs  with 
Congenital  ^^^  degree  of  frequency,  namely,  syphilis. 
Plac  Nevertheless,  a  child  may  be  born  with 

Infection.      3,lmost  any  of  the   infectious  diseases   if 

the  mother  is  suffering  at  the  time  from  the 
same.  Thus,  in  the  new-born  has  occurred  typhoid 
fever,  small-pox,  scarlet  fever,  tuberculosis,  etc.  In 
the  case  of  tuberculosis,  however,  it  is  surprising  how 
very  rarely  the  disease  is  found  in  the  children  of  a 
consumptive  mother;  in  fact  congenital  tuberculosis 
is  so  uncommon,  that  tuberculosis  is  not  regarded  by  the 
profession  as  an  hereditary  disease. 


PORTALS  OF  ENTRY  OF  INFECTIOUS  AGENTS.     183 

The  discharges  from  syphilitic  lesions  in  the  infant 
are  highly  dangerous  to  everyone  who  handles  it  except 
its  mother.  In  such  children  sores  of  the  mouth  are 
common,  and  wet-nurses  have  frequently  been  known 
to  contract  the  disease  from  suckling  them. 

Cryptogenic  infections  refer  to  those  deep- 
Cryptogenic.  seated   affections   for  which   a  portal   of 

entry  cannot  be  found.  Endocarditis  (in- 
flammation of  the  heart  valves),  osteomyelitis  (inflam- 
mation of  bone),  etc.,  are  illustrations  of  this  type  of 
infection. 


CHAPTER  VIII. 

PORTALS  OF  ENTRY  AND  AVENUES  OF  EXIT 

OF  MICRO-ORGANISMS  IN  THE  VARIOUS 

DISEASES. 

Actinomycosis  (''lumpy-jaw,"  "wooden  tongue"); 
disease  of  man  and  domestic  animals,  particularly 
bovines. 

(a)  Cause:  Actinomyces    hovis    (ray- fungus) ;   jorms 

spores. 

(b)  Localized:  Lungs,  bowels,  subcutaneous  tissues; 

often  about  jaw  or  tongue. 

(c)  Entry:  Through    mouth    and    nose  with   food; 

through  wounds. 

(d)  Exit:  Sputum,    feces,   and    pus    from    lesions. 

^(e)  Contracted:  Doubtful  whether  can  be  communi- 
cated directly,  either  from  animal  to 
man,  or  from  man  to  animal.  Barley,  oats, 
or  rye,  seem  to  be  vehicles  for  the  fungus. 

(f)  Disinfection:  Since  the  actinomyces  form  spores, 

disinfecting  agents  are  same  as  for  anthrax 

and  tetanus. 

The  ray-fungus  can  be  seen  with  the  naked  eye  in 

the  pus  and  secretions  of  lesions  as  whitish  or  yellow- 

184 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.     185 

ish  bodies  that  have  the  appearance  of  fine  grains  of 
sulphur;  seen  best  if  a  small  quantity  of  the  pus  is 
pressed  between  two  slides  or  watch  crystals. 

Anthrax  (Wool-sorter's  Disease,  malignant  pus- 
tule, splenic  fever) ;  disease  of  man  and  domestic  ani- 
mals, especially  sheep  and  cattle. 

(a)  Cause:  Bacillus  anthracis;  forms  spores. 

(b)  Localization:   Subcutaneous    tissues   (malignant 

pustule) ;  lungs  (wool-sorter's  disease) ;  in- 
testinal tract;  all  of  these  lead  to  bacter- 
iaemia  (bacteria  in  blood)  in  vast  majority 
of  cases. 

(c)  Entry:  Through  wounds  or  abrasions;  through 

mouth,  eating  meat  or  drinking  milk  of 
infected  animals ;  through  respiratory  tract 
(inhaled    in    dust — wool-sorter's  disease). 

(d)  Exit:  Expectoration    in    pulmonic    form;    pus 

from  abscess  in  local  form;  discharges 
from  bowels  in  intestinal  form. 

(e)  Contracted:   By  inhalation    in   sorting  wool   of 

infected  animals;  by  abrasion  or  wound 
in  handling  flesh  or  hides  of  infected  ani- 
mals; by  eating  flesh  or  drinking  milk 
of  diseased  animals;  by  the  soiling  of 
wounds   or  food-stuft's  by   infected  flies. 

(f)  Disinfection    and    Prophylaxis:     Forms   spores, 

therefore  unusual  precautions  are  to  be 
used.     Burn  cadavers,  and  contaminated 


i86       INFECTIOUS  AND  PARASITIC  DISEASES. 

bedding,  cloths,  etc.,  where  this  is  possible; 
where    destruction    is    not    feasible,    use 
(i)  Super-heated  steam  (15  pounds  pressure),  15 
minutes. 

(2)  Tricresol,  or  lysol,  2  per  cent  solution,  for  two 

hours. 

(3)  Bichloride  of  mercury  (1-500),  for  one  hour. 

(4)  Formalin,  15  per  cent  solution,  one  and  one- 

half  hours. 

(5)  Boiling  water,  or  steam,  for  two  hours. 

Bubonic  Plague  (la  peste,  black  death,  etc.). 

(a)  Cause:  Bacillus  pestis;  non-sporogenous. 

(b)  Localized:     Skin     and    subcutaneous    tissues; 

lymph-glands;  lungs;  and  intestinal  tract. 

(c)  Entry :  Wounds  of  skin ;  nose  and  mouth  through 

air;  mouth  in  food  and  water. 

(d)  Exit:  In  any  of  the  discharges  from  situation 

where  disease  is  localized;  therefore,  sup- 
purations, suppurating  buboes,  abscesses, 
blisters,  sputum,  vomit,  feces,  urine. 

(e)  Contracted:    By     inhalation     through     contact 

with  sick;  through  wounds  contaminated 
or  caused  by  infected  fleas,  flies,  ants, 
etc.,  also  food  and  water  contaminated  by 
the  sick,  or  infected  vermin,  e.g.,  rats, 
mice,  etc. 

Note  : — Use  all  chemical  disinfectants  at  or  near  the  boiling  point. 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.     187 

(f)  Disinfection:  Must    be    thorough;  bacillus    not 

difficult  to  destroy;  disinfect  sputum, 
dejecta,  urine,  etc.,  with  5  per  cent  carbolic, 
3-5  per  cent  formalin,  2  per  cent  tricresol, 
or  boiling  water  the  same  as  for  other 
non-sporogenous  bacteria.  Wash  body  of 
patient,  hands,  and  objects  with  i-iooo 
bichloride  of  mercury.  Fumigate  with  sul- 
phur dioxide  on  account  of  its  destructive 
action  on  vermin. 

(g)  Prophylaxis:  Vermin,  particularly  rats  and  mice, 

are  susceptible  to  plague ;  indeed,  the  former 
are  believed  to  be  the  principle  carriers  of  it. 
They  infect  the  ground,  dwellings,  foods,  and 
water.  Therefore,  safety  lies  in  the  destruc- 
tion of  all  vermin  in  the  houses.  As  dogs 
and  cattle  are  also  susceptible  to  the  disease, 
they  should  be  carefully  protected  from 
exposure.  Screen  dwelling  and  rooms; 
since  the  ground  becomes  infected  by  rats, 
and  infected  excreta,  and  because  wounds 
of  the  feet  and  legs  are  frequent  portals  of 
entry  for  the  specific  bacillus,  the  constant 
wearing  of  shoes  and  leggins  is  a  wise 
prophylactic. 
The  pneumonic  form  of  plague  is  especially  danger- 
ous to  attendants  because  the  bacilli  are  thrown  out 
in  the  spray  in  coughing  and  sneezing.     Eat  nothing 


i88       INFECTIOUS  AND  PARASITIC  DISEASES. 

raw,  such  as  milk,  butter,  cheese,  etc. ;  serve  everything 
hot.  Eschew  all  fresh  fruits  and  vegetables.  Neither 
wash  in,  nor  drink  of,  unboiled  water.  The  bodies  of 
those  succumbing  to  the  disease  should  be  cremated. 
Clothing,  sheets,  etc.,  may  be  disinfected  with  solu- 
tions above  given  for  sputum.  Mop  all  surfaces  in 
the  sick-room  frequently  with  a  solution  of  bichloride 
of  mercury  (i-iooo).  Rigid  isolation  and  quarantine 
should  be  instituted. 

Epidemic  Cerebro-spinal  Meningitis. 

(a)  Cause:  Diplococcus   intracellularis  meningitidis; 

non-sporulating. 

(b)  Localization:  Membranes   of  brain   and  spinal 

cord. 

(c)  Entry:  Probably  nose  by  inhalation. 

(d)  Exit:  Probably  nasal  secretions. 

(e)  Contracted:  Does  not  seem  directly  contagious 

from  sick  to  well,  nor  by  fomites. 

(f)  Disinfection  and  Prophylaxis:  Disinfect  all  secre- 

tions and  discharges,  and  all  objects  that 
have  been  in  contact  with  patient.  Pro- 
tect patient,  and  all  articles  that  have  been 
in  contact  with  patient,  from  insects ;  there- 
fore screen  against  flies,  mosquitoes,  etc. 

Chicken-pox  (varicella). 

(a)  Cause:  Not  known. 

(b)  Localization:  Same  as  small-pox. 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.     189 

(c)  Entry:  Probably  through  respiratory  tract  (inha- 

lation). 

(d)  Exit:  Exhalations  from  lungs  and  skin,  particu- 

larly in  the  dried  scales  of  the  latter;  in  all 
secretions  and  excretions,  therefore,  spu- 
tum, feces,  urine,  tears,  nose,  etc. 

(e)  Contracted:  Highly  contagious. 

(f)  Disinfection:  Same  as  applied  to  small-pox. 

(g)  Prophylaxis:  Same  as  in  small-pox. 

Cholera. 

(a)  Cause:  Spirillum     cholem     AsiaticcE     (Koch), 

' '  comma  bacillus ; ' '  non-sporogenous . 

(b)  Localization:  Small  and  large  intestines. 

(c)  Entry:  Mouth  in  water  and  food. 

(d)  Exit:  Discharges    from    bowels,    sometimes    in 

vomit. 

(e)  Contracted:  Is  usually  water-borne  infection,  but 

may  come  from  foods  contaminated  either 
by  soiled  hands,  human  fertilizer,  or  by  in- 
sects which  have  been  in  contact  with  dis- 
charges containing  the  spirilla. 

(f)  Disinfection:  Spirillum  has  slight  resisting  powers, 

65°  C.  (149°  F.)  kills  in  five  minutes,  100°  C. 
(212°  F.),  destroying  it  at  once;  disinfect 
stools  and  vomited  matter  with  5  per  cent 
solution  formalin,  5  per  cent  solution  car- 
bolic acid,  2  per  cent  tricresol,  or  twice  their 


I90       INFECTIOUS  AND  PARASITIC  DISEASES. 

amount  with  milk  of  lime;  treat  bed-linen, 
etc.,  same  as  in  typhoid;  fumigation  not 
necessary  if  appropriate  sick-room  precau- 
tions are  taken. 

(g)  Prophylaxis:  When  cholera  prevails,  do  not  eat 
any  fruits  or  vegetables  rav^;  boil  all 
water,  whether  used  for  drinking  purposes 
or  for  washing  of  utensils;  cook  all  foods 
well,  and  leave  nothing  exposed  to  the  air, 
best  to  serve  everything  hot ;  protect  sick- 
room, and  all  houses  from  flies,  and  keep 
free  from  insects.  If  these  precautions 
are  followed,  one  can  live  in  a  cholera 
infected  town  and  nurse  cholera  patients 
without  danger  of  contracting  the  disease. 

Dengue  (break-bone  fever,  dandy  fever). 

(a)  Cause:  Unknown. 

(b)  Entry  and  Exit:  Not  known. 

(c)  Disinfection:  Not    practised,    since    as    far    as 

known  it  never  proves  fatal. 

Diphtheria. 

(a)  Cause:  Bacillus  diphtherice  (Klebs-Loeffler  bac- 

illus). 

(b)  Localization:  All   mucous    membranes,   usually 

tonsils,  pharynx,  and  anterior  and  pos- 
terior nares;  occurs  in  larynx,  when  it  is 
called  membranous  croup;  sometimes  seen 
on  the  vulva;  may  infect  wounds. 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.     191 

(c)  Entry:  By  mouth  and  nose  through  air,  or  by 

mouth  through  contaminated  foods  or 
objects;  only  the  air  around  the  patient 
is  dangerous,  which  is  made  infectious 
through  coughing,  sneezing,  and  careless 
disposal  of  secretions  from  infected  por- 
tion; through  wounds  uncommon. 

(d)  Exit:  Discharges    from    nose,    mouth,  pharynx 

and  larynx;  also  from  eye  and  vulva  if 
disease  situated  there. 

(e)  Contracted:  Is    highly    contagious,    spread    by 

contact  with  the  sick  chiefly,  ito  a  less 
extent  through  fomites;  kissing,  handker- 
chiefs, towels,  toys,  etc.,  may  all  convey 
the  infection. 

(f)  Disinfection:  Boiling  water  kills  the  diphtheria 

bacillus  at  once;  direct  sun-light  is  also 
effective  in  about  an  hour ;  disinfect  sputum, 
nasal  discharge,  linens,  utensils,  etc.,  with 
boiling  water,  or  with  tricresol  (2  per  cent), 
formalin  (5  per  cent),  carbolic  acid  (5  per 
cent) ;  wipe  all  surfaces  in  room  (including 
floor)  with  bichloride  of  mercury  (i-iooo) 
daily,  fumigate  with  sulphur  or  formalde- 
hyde. 

(g)  Prophylaxis:  Isolation  of   sick,    no  matter  how 

slight  the  infection,  since  there  is  no  ques- 
tion that  diphtheria  is  spread  by  the  mild 


192       INFECTIOUS  AND  PARASITIC  DISEASES. 

or  unsuspected  cases;  those  in  contact 
with  the  patient  should  use  antiseptic 
gargle,  disinfect  hands,  and  avoid  getting 
in  the  way  of  spray  of  expectoration ;  fumi- 
gate with  sulphur  or  formaldehyde. 

Amoebic  Dysentery  (chronic  tropical  dysentery). 

(a)  Cause:  Amceba  dy sentence,   an  animal  parasite. 

(b)  Localization:  Intestinal  tract. 

(c)  Entry:  Mouth  through  water,  fresh  fruits,  and 

vegetables. 

(d)  Exit:  Evacuations  from  bowels. 

(e)  Contracted:  From  infected  water,  etc. 

(f)  Disinfection:  Only  the  stools  need  be  disinfected, 

using  the  same  solutions  as  in  typhoid. 

(g)  Prophylaxis:  Boil  all  water  where  the  disease 

prevails. 

Bacillary  Dysentery  (acute  epidemic  dysentery). 

(a)  Cause:  Bacillus  dy  sentence  (Shiga);  non-sporog~ 

enous. 

(b)  Localization:  Intestines. 

(c)  Entry:  Mouth,  through  water  and  foods. 

(d)  Exit:  In  evacuations  from  the  bowels;  may  be 

present  in  vomit. 

(e)  Contracted:  Same  as  typhoid. 

(f)  Disinfection:  As  far  as  known  only  the  stools 

have  to  be  disinfected;  the  bacillus  has 
about  the  same  resisting  qualities  as  the 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.     193 

typhoid  bacillus,  the  strengths  given  for  the 
various  disinfectants  in  typhoid  being 
sufficient, 
(g)  Prophylaxis:  When  the  disease  prevails  boil  all 
water  and  cook  well  all  foods;  eat  neither 
fruits  nor  vegetables  raw;  use  same  pre- 
cautions as  in  typhoid. 

Erysipelas. 

(a)  Cause:  Streptococcus   pyogenes;   does    not  form       j^ 

spores. 

(b)  Localization:  Skin,  or  any  wound  that  becomes 

infected  with  the  micro-organism. 

(c)  Entry :  Wounds  or  abrasions  of  skin  and  mucous 

membranes. 

(d)  Exit :  In  pus  and  secretions  from  the  seat  of  the 

inflammation ;  also  probably  in  the  desqua- 
mating skin  from  an  inflamed  area. 

(e)  Contracted :  Is  highly  contagious  to  any  one  with 

a  wound;  to  a  woman  about  to  he  confined^ 
or  in  the  puerperium;  may  be  conveyed  by 
fomites,  instruments,  etc. 

(f)  Disinfection:  100°  C.  (212°  F.)  moist,  kills  the 

streptococcus  at  once;  all  discharges 
should  be  disinfected  with  the  solutions  in 
the  strengths  recommended ;  urine  should 
certainly  be  disinfected ;  room,  patient,  and 
bedding,  clothing,  etc.,  should  be  treated 
13 


194       INFECTIOUS  AND  PARASITIC  DISEASES. 

as  for  small-pox;  fumigate  with  formalde- 
hyde or  sulphur, 
(g)  Prophylaxis :  Isolate  the  patient  and  his  attendant ; 
latter  should  have  nothing  to  do  with  opera- 
tions, confinements,  etc.,  during  the  period 
of  attendance  on  a  case  of  erysipelas,  and 
for  two  weeks  thereafter;  during  the  lat- 
ter period,  daily  disinfection  of  the  hands, 
hair,  and  person  generally  should  be  fol- 
lowed; room  where  patient  has  been 
should  be  thoroughly  cleansed  and  dis- 
infected. 

Glanders. 

(a)  Cause:  Bacillus  mallei;  is  non-sporogenous. 

(b)  Localization:  Exposed    surfaces    of    the    body 

(farcy),  or  mucous  membranes  of  the  nose. 

(c)  Entry:  Wounds  of  skin,  or  mucous  membrane 

of  nose. 

(d)  Exit:  Purulent  discharges  from  nose;  ulcers  and 

abscesses;  expectoration;  urine. 

(e)  Contracted :  Usually  by  contact  with  diseased  an- 

imals (horses  and  asses),  or  hides  of  same 
through  abrasions  of  skin. 

(f)  Disinfection:  Easily  destroyed  by  boiling,  or  the 

usual  strengths  of  carbolic  acid,  formalin, 
or  tricresol. 

(g)  Prophylaxis:  Consists  in  the  destruction  of  all 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.     195 

diseased  animals,  and  thorough  disinfection 
of  the  discharges  and  soiled  dressings  of 
infected  individuals. 

Gonorrhoea. 

(a)  Cause:  Micrococcus   gonorrhcecE-   (Neisser);  non- 

sporogenous. 

(b)  Localized :  Urethra  (gonorrhoea,  specific  urethri- 

tis, clap);  eye  (gonorrhoeal  ophthalmia, 
ophthalmia  neonatorum);  vagina;  blood; 
joints;  etc. 

(c)  Entry:     Urethra,     eye,     vagina,     occasionally 

wounds.  I 

(d)  Exit:  In  suppurations  from  diseased  tissues  or 

organs.  L. 

(e)  Contracted:  In  urethra  and  vagina  from  irregu- 

lar intercourse;  in  eyes  of  adults  from  pol- 
luted fingers  or  towels,  etc.;  in  new-born 
during  birth ;  in  female  children  the  vagina 
■is  infected  through  soiled  sponges,  wash- 
cloths, etc. 

(f)  Disinfection:  Micro-organism    has    slight  resist- 

ance; boiling  kills  it  at  once.  Ordinary 
disinfectants  effective  in  the  percentages 
in  which  used  for  vegetative  forms  of  other 
bacteria. 

(g)  Prophylaxis:  Males  with  acute  or  chronic  gon- 

orrhoea   (gleet)    should    not   marry   until 


196       INFECTIOUS  AND  PARASITIC  DISEASES. 

cured.  Individuals  with  the  disease  should 
be  warned  of  the  awful  danger  consequent 
upon  eye  infection.  The  children  born  of 
immoral  mothers,  and  all  born  among  the 
lowest  classes,  should  have  instilled  into 
each  eye  immediately  after  birth  one  to  two 
drops  of  a  I  per  cent  solution  of  nitrate  of 
silver. 

Hydrophobia  (Rabies,  Lyssa). 

(a)  Cause:  Unknown. 

(b)  Locahzed:  Wounds,  primarily; secondarily,  brain 

and  spinal  cord. 

(c)  Entry:  Through  wounds. 

(d)  Exit:  Saliva. 

(e)  Contracted:  Through  bite  of  mad  animal,  such 

as  dog,  wolf,  cat,  etc.  Novi  says,  "that 
midges  and  flies  are  capable  of  conveying 
the  infection." 

(f)  Disinfection:  Saliva,  and  linens,  beddings,  etc., 

soiled  by  saliva,  should  be  boiled,  or  dis- 
infected with  one  of  the  solutions  advised 
for  other  diseases. 

(g)  Prophylaxis :  Kill  all  mad  animals,  and  all  others 

bitten  by  same.  Dogs  should  be  muzzled. 
Bites  of  all  animals  should  be  carefully 
washed  and  thoroughly  cauterized  with 
concentrated  carbolic  acid,  or  a  glowing 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.     197 

poker.  Previously,  oral  suction  may  be 
practised.  Keep  wound  open  for  from  five 
to  six  weeks. 

Influenza  (La  Grippe,  Russian  fever). 

(a)  Cause:  Bacterium  in fluenziB;  is  non-sporogenous. 

(b)  Localized:  Throat;  nose;  lungs;  blood. 

(c)  Entry:  By  air  through  mouth  and  nose. 

(d)  Exit:  Discharges  from  nose,  throat,  and  lungs. 

(e)  Contracted :  Probably  entirely  by  contact  with  the 

sick. 

(f)  Disinfection:  Bacilli    are    quickly  destroyed  by 

even  weak  solutions  of  the  ordinary  disin- 
fectants; at  once  by  boiling;  fumigate  with 
formaldehyde  or  sulphur. 

(g)  Prophylaxis :  Since  influenza  is  a  serious  disease 

in  the  case  of  the  very  young  and  the  aged, 
and  furnishes  a  large  proportion  of  the 
mortality  at  these  periods  of  life,  the  nasal 
and  bronchial  secretions  should  be  care- 
fully disinfected  in  every  case. 

Leprosy. 

(a)  Cause:  Bacillus  leprce;  non-sporogenous. 

(b)  Localized:  Mucous  membranes  and  skin  gener- 

ally; nervous  system. 

(d)  Exit :  In  suppurations  from  broken-down  nodules 

of  nose,  mouth  and  skin. 

(e)  Contracted:  Contracted    with  difficulty.     Long, 


198       INFECTIOUS  AND  PARASITIC  DISEASES. 

intimate  contact  seems  essential.  Atten- 
dants need  have  no  fear  of  contracting  the 
disease,  if  reasonable  precautions  are 
taken. 

(f)  Disinfection :  Not  known,  since  germ  has  never 

been  cultivated  outside  the  body;  prob- 
ably same  as  for  tuberculosis. 

(g)  Prophylaxis:  Cleanliness;    disinfection    of    dis- 

charges from  suppurations  and  soiled 
linens,  etc. ;  segregation  of  lepers. 

Madura  Foot  (mycetoma,  Madura  disease,  pied  de 
Madura). 

(a)  Cause:  Streptothrix  madurae,  forms  spores  (?). 

(b)  Localization:  Usually  feet,  but  may  affect  other 

portions  of  body. 

(c)  Entry:  Through  wounds  in  skin. 

(d)  Exit:  In  discharges  from  broken-down  nodules. 

(e)  Contracted:  In   countries  where   the   disease  is 

common,  is  attributed  to  prick  of  a  thorn; 
is  probably  not  communicated  from  man 
to  man. 

(f)  Disinfection:  Should    be    same    as    for  anthrax 

and  tetanus. 

Malarial  Fever  (ague,  intermittent  fever). 

(a)  Cause:  H cematozoa  malaricB  (sporozo^). 

(b)  Localized :  In  blood  and  tissues. 

(c)  Entry:  Only  through  bites  of  mosquitoes. 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.     199 

(d)  Exit :  In  the  blood  solely  through  bites  of  mos- 

quitoes. 

(e)  Contracted:  By  being  bitten  by  that  species  of 

mosquito  (Anopheles)  which  acts  as  host 
for  the  parasite. 

(f)  Disinfection:  Consists  in  the  destruction  of  mos- 

quitoes by  an  insecticide  in  the  bed-room 
of  the  sick.  Pyrethrum,  two  pounds  to  each 
one  thousand  cubic  feet.  Sulphur,  one 
pound  to  each  two  thousand  cubic  feet. 
Where  sulphur  used,  two  hours'  exposure 
sufficient,  and  moisture  (which  decolorizes 
and  destroys  fabrics)  not  necessary.  As 
pyrethrum  only  stuns  the  knats  they  must 
be  gathered  up  and  burned  after  fumigat- 
ing. 

(g)  Prophylaxis :  Where  malaria  is  prevalent,  screen 

rooms  and  houses  with  fine  mesh  screens 
to  keep  mosquitoes  out;  chief  danger  is  at 
night,  since  anopheles  is  nocturnal  in 
its  habits.  Anopheles  breeds  in  shallow 
puddles  and  ditches,  in  which  places  the 
young  can  be  destroyed  by  sprinkling  sur- 
face of  water  with  coal-oil  about  every  two 
weeks.  Two  grains  of  quinine  three  times 
daily  is  also  a  wise  precaution. 

Measles. 

(a)  Cause:  Unknown. 


200       INFECTIOUS  AND  PARASITIC  DISEASES. 

(b)  Localization:  Eyes,    nose,    mouth,   throat,   and 

skin. 

(c)  Entry:  Probably  air  borne  to  mouth  or  nose. 

(d)  Exit :  Oculo-nasal  secretions,  saliva,  breath  and 

desquamated  skin. 

(e)  Contracted:  By  contact  with  sick  through  air; 

fomites ;  third  person. 

(f)  Disinfection;  Same  as  for  small-pox. 

(g)  Prophylaxis:  Same  as  for  small-pox. 

Mumps  (epidemic  parotitis). 

(a)  Cause:  Unknown. 

(b)  Locahzed:  One  or  both  parotid  glands. 

(c)  Entry:  Probably  mouth. 

(d)  Exit:  Supposedly,  in  saliva. 

(e)  Disinfection    and    Prophylaxis:    Only    sputum 

need  be  disinfected;  however,  because  in 
the  army  the  efficiency  is  severely  taxed  by 
the  orchitis  which  so  commonly  occurs 
with  mumps  in  adults,  isolation  and  dis- 
infection as  for  other  contagious  diseases 
should  be  practised. 

Pneumonia  (Lobar  pneumonia). 

(a)  Cause:  Diplococcus  pneumonice  (pneumococcus, 

micrococcus  lanceolatus) ;  is  non-sporogen- 
ous. 

(b)  Localization:  Lungs;    by    extension,   in  blood, 

pleural  cavity  and  pericardium. 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.    201 

(c)  Entry:  Respiratory  channels ;  normally  present  in 

almost  everyone's  mouth. 

(d)  Exit:  Sputum;    in    discharges    when   empyema 

(secondary  to  pneumonia)  ruptures,  or 
is  opened  by  operation;  in  complications, 
otitis  media,  etc. 

(e)  Contracted:  Exposure  to  cold  and  wet;  exposure 

to  pneumonia  while  fatigued  and  depressed. 

(f)  Disinfection:  Easily   destroyed   by  boiling;  car- 

bolic acid  3-5  per  cent,  formalin  3-5 
per  cent,  tricresol  i  per  cent.  Sulphur  or 
formaldehyde  fumigation. 

(g)  Prophylaxis:  January,    February,   and    March, 

are  the  coldest  and  most  disagreable  months 
in  the  year  and  are  on  this  account  the 
months  in  which  the  greatest  number  of 
cases  of  pneumonia  occur.  Avoid  wetting 
and  exposure,  and  especially  after  ''catch- 
ing cold. "  Intoxicated  persons  are  partic- 
ularly susceptible  to  pneumonia,  as  are 
also  infants,  old  people,  and  those  debili- 
tated by  a  chronic  disease.  Mental  de- 
pression is  also  a  predisposing  cause. 

Relapsing  Fever  ("Famine  fever,"  seven-day  fever, 
etc.). 

(a)  Cause:  Spirochceta  Obermeieri. 

(b)  Localization:  Blood. 


202       INFECTIOUS  AND  PARASITIC  DISEASES. 

(c)  Entry:  Not    known,   probably  through    bite    of 

insect,  e.g.,  bed-bug. 

(d)  Exit:  Probably  through  bite  of  suctorial  insect. 

(e)  Contracted :  Seems  to  be  contagious ;  but  as  only 

seen  where  over-crowding,  and  where 
hygienic  conditions  are  bad,  probably 
conveyed  by  insect. 

(f)  Disinfection :  Nothing  known  of  the  micro-organ- 

ism outside  of  the  body. 

(g)  Prophylaxis:   Plenty    of    fresh    air,   good  food, 

and  personal  cleanliness,  are  probably  the 
best  means  of  avoiding  the  infection. 
Screen  houses  against  mosquitoes,  flies, 
etc.,  and  wage  war  against  all  vermin  such 
as  bed-bugs,  roaches,  etc. 

Rubella  (Rotheln,  German  measles). 

(a)  Cause:  Not  known. 

(b)  Localization:  Blood,  skin,  respiratory  tract. 

(c)  Entry:  Probably  through  respiratory  tract. 

(d)  Exit :  Respiratory  tract  and  probably  emanations 

from  skin. 

(e)  Contracted:  Resembles  measles  (which see). 

Scarlet  Fever. 

(a)  Cause:  Not  known. 

(b)  Localized :  Throat ;  blood ;  skin ;  in  complicating 

suppurations,  e.g.,  ear. 

(c)  Entry:  Respiratory  tract;  also  wounds. 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.    203 

(d)  Exit:  Sputum;    nasal    secretions;    skin,    before 

and  during  exfoliation;  suppurations  dur- 
ing and  following  the  disease. 

(e)  Contracted:  Contact  with  the  disease,  or  with 

persons  and  objects  which  have  been  in 
contact  with  same;  from  milk  handled  by 
persons  sick  or  convalescent  from  scarlatina; 
from  individuals  with  suppurations  con- 
sequent upon  an  attack,  e.g.,  otitis  media 
(middle-ear  disease). 

(f)  Disinfection:  Virus  has  unusual  vitality;  disin- 

fect same  as  for  small-pox  or  diphtheria. 

(g)  Prophylaxis:  Quarantine  should  not  be  less  than 

forty  days  after  the  completion  of  desqua- 
mation, and  it  might  even  be  continued 
longer;  air-passages  should  be  treated 
antiseptically  during  whole  period  of 
quarantine.  Discharging  ear  is  infectious, 
and  children  with  such  a  discharge  have 
been  known  to  transmit  the  disease  in  this 
way.  Sun  and  air  room  some  weeks 
after  case.  Most  rigid  quarantine  and 
disinfection  must  be  practised  to  prevent 
contagion. 

Small-pox  (variola). 

(a)  Cause:  Not  known. 

(b)  LocaHzation:  Skin,  conjunctivae,  mouth,  oesopha- 


204       INFECTIOUS  AND  PARASITIC  DISEASES. 

gus,  rectum,  and  probably  blood ;  is  general 
infection. 

(c)  Entry:    Probably     through     respiratory     tract; 

may  also  enter  through  abrasions,  as  the 
former  practice  of  variolation  proves. 

(d)  Exit:  Exhalations  from  lungs  and  skin,  partic- 

ularly in  the  dried  scales  of  the  latter; 
in  all  secretions  and  excretions,  therefore 
in  sputum,  urine,  feces,  tears,  pustules,  etc. 

(e)  Contracted:  Highly  contagious;  virus   is   in  air 

surrounding  patient,  being  thrown  off  with 
breath  and  wafted  from  eruption;  is  con- 
veyed by  persons  and  f omites ;  may  also  be 
conveyed  by  flies . 

(f)  Disinfection:    Disinfect    everything   which    has 

been  in  contact  with  patient;  also  en- 
tire room  and  contents.  Screen  windows 
from  flies,  and  kill  all  vermin;  wipe  all 
surfaces  of  room  daily  with  bichloride 
of  mercury  (i-iooo);  linens,  etc.,  boil, 
steam,  or  immerse  in  tricresol  (2  per  cent), 
formalin  (5  per  cent),  carbolic  acid  (5  per 
cent) ;  anoint  patient  with  carbolated  vase- 
lin;  all  abscesses  and  ulcers  should  be 
regarded  as  infectious  until  healed;  fumi- 
gate after  recovery  with  sulphur  or  for- 
maldehyde. 

(g)  Prophylaxis:  Vaccination    of  every  one    during 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.    205 

an  epidemic,  whether  previously  vaccinated 
or  not;  isolation  of  sick,  and  disinfection 
of  patient  and  room  after  recovery. 

Epidemic  Stomatitis  (aphthous  fever,  foot  and  mouth 
disease);  is  disease  of  cattle,  sheep,  and  pigs,  which 
is  often  transmitted  to  man. 

(a)  Cause:  Unknown. 

(b)  Localization:  Mucous  membrane  of  mouth  and 

lips;  also  in  wounds;  in  cattle  also  on  tits 
and  udder. 

(c)  Entry:  Mouth    through    milk,  and    wounds    of 

hands,  arm,  and  fore-arm  from  infected 
animal. 

(d)  Exit :  From  secretions  of  mouth,  and  ulcers  of  the 

disease. 

(e)  Contracted:  Contracted    from    pustules  of    sick 

animal,  or  from  milk,  butter  and  cheese. 

(f)  Disinfection:  Disinfect    secretions    from  mouth, 

also  discharges  from  the  lesions  of  the 
disease,  bandages,  linens,  etc.,  in  the  usual 
strengths  of  the  solutions  given  for  other 
diseases. 

(g)  Prophylaxis :  Where  epidemic  in  cattle,  boil  all 

milk,  and  isolate  all  sick  cattle;  also  indi- 
viduals who  take  care  of  them ;  butter  and 
cheese  made  from  milk  of  infected  animals 
can  also  convey  the  disease. 


2o6       INFECTIOUS  AND  PARASITIC  DISEASES. 

Syphilis  (Lues). 

(a)  Cause:  Spirochceta  pallidce  {?). 

(b)  Localization:  Practically  everywhere    in  second 

and  third  stages;  in  first  stage  (primary) 
the  initial  lesion  (chancer)  is  usually 
upon  the  genitals;  extra-genital  chancers, 
however,  may  be  found  upon  any  cutan- 
eous surface;  also  upon  lips,  tongue,  ton- 
sils, eye-lids,  or  rectum. 

(c)  Entry:  Through   abrasions  of   skin  or  mucous 

membrane ;  through  spermatozoan ;  through 
ovum;  placenta. 

(d)  Exit:  From  discharging  lesions,  and  with  blood 

when  drawn. 

(e)  Contracted:  Usually  through   illicit  intercourse, 

when  primary  lesion  is  found  upon  gen- 
ital organs ;  may  be  innocently  contracted 
through  kissing,  from  infected  handker- 
chiefs, pipes,  dishes,  etc.;  by  pricking 
finger  during  operation  upon  a  syphilitic, 
or  through  examination  during  confine- 
ment. When  innocently  contracted  is 
called  syphilis  insontium  to  distinguish 
it  from  venereal  syphilis,  which  carries 
with  it  an  implied  stigma. 

(f)  Disinfection :  Boiling  water  or  steam ;  usual  chem- 

ical disinfectants. 

(g)  Prophylaxis:  Abstinence  from  irregular  relations ; 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.     207 

physicians  should  impress  upon  all  syphil- 
itics  the  danger  to  others  of  contracting 
the  disease  from  discharges  from  both  the 
primary  (chancer)  and  secondary  (mucous 
patches,  ulcers,  particularly  of  throat) 
lesions. 

Tetanus  (Lock-jaw). 

(a)  Cause:  Bacillus  tetani;  forms  spores. 

(b)  Localized :  Subcutaneous  or  sub-mucous  tissues ; 

usually  former;  umbilical  cord  of  new- 
born. 

(c)  Entry :  Wounds,  often  of  trifling  nature ;  also  in 

wounds  where  much  tearing  of  tissue 
has  occurred,  especially  if  soiled  with 
earth;  compound  fractures. 

(d)  Exit:  In  discharges  from  wound  only. 

(e)  Contracted :  Gun-shot  or  cannon-cracker  wounds ; 

contusions  in  which  powder,  earth  or  other 
foreign  bodies  driven  into  tissues;  punc- 
tured wounds  of  hands  or  feet,  e.g.,  by 
nail. 

(f)  Disinfection:  As  forms  spores,  prolonged  boiling 

or  contact  with  powerful  disinfectants 
necessary,  tricresol  or  lysol  2  per  cent  solu- 
tion, two  hours;  bichloride  of  mercury 
1-500,  two  hours.  Use  solutions  hot. 
Only  discharges  from  wound,  and  soiled 


2o8       INFECTIOUS  AND  PARASITIC  DISEASES. 

dressings,  need  be  disinfected.  See  an- 
thrax (p.  185). 
(g)  Prophylaxis:  Consists  in  thorough  opening  and 
cleansing  of  all  wounds  which  have  been 
soiled  with  earth,  or  resulted  from  Fourth 
of  July  celebrations;  or  in  which  foreign 
body  is  imbedded  in  flesh.  Where  tet- 
anus is  feared,  the  wound  should  not  be 
sealed  with  dressings,  but  left  exposed  to 
the  air;  tetanus  antitoxin  should  he  used. 

Tuberculosis. 

(a)  Cause:    Bacillus    tuberculosis    (Koch    bacillus); 

non-sporogenous,  but  exhibits  greater  resist- 
ance to  destructive  agencies  than  vegetative 
forms  of  other  bacteria. 

(b)  Localized:  Practically  everywhere;  lungs  (phthi- 

sis, consumption) ;  lymph  glands  (scrofula) ; 
bones,   abdominal  viscera;  brain,   etc. 

(c)  Entry:  Chiefly  by  air-passages,  and  by  mouth 

with  food  and  drink;  also  through  wound 
of  skin  and  mucous  membranes. 

(d)  Exit:  In  all  discharges  from  diseased  tissues  or 

organs.  As  lungs  most  frequently  are 
the  seat  of  the  disease,  the  sputum  is  the 
most  common  vehicle  of  discharge. 

(e)  Contracted:  Usually   by   inhalation  where  pro- 

longed contact  with  consumptive ;  probable 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.    209 

that  infants  occasionally  contract  the  dis- 
ease by  drinking  milk  from  tuberculous 
cows. 

(f)  Disinfection:  Boil    infected    material    in    closed 

vessel  ten  minutes  or  longer;  well  to  burn 
objects  of  no  value.  For  sputum,  formalin 
15-20  per  cent,  tricresol  2  per  cent,  lysol 
2  per  cent  are  recommended;  mix  these 
thorougly  with  sputum  and  let  stand  one 
hour.  Fumigate  with  sulphur  or  formal- 
dehyde. 

(g)  Prophylaxis:  Chief  danger  is  from  carelessness 

of  the  consumptive  in  disposal  of  sputum; 
if  careful  disinfection  of  expectoration 
and  all  things  soiled  during  the  act  of  sneez- 
ing, coughing,  etc.,  is  practised,  he  is  no 
menace  to  others.  Those  immediately 
surrounding  the  consumptive  most  often 
fall  victims,  a  fact  better  established  than 
heredity  in  this  disease.  Neither  milk 
nor  meat  from  tuberculous  cattle  should 
be  used.  Consumptives  should  refrain 
from  kissing  others ;  nor  should  they  marry. 

Typhoid  Fever. 

(a)  Cause:  Bacillus  typhosus;  is  non-sporogenous. 

(b)  Localization:  Primarily    in    intestinal    tract   or 

lungs;  in  blood;  bladder;  in  complicatmg 
suppurations. 


14 


2IO       INFECTIOUS  AND  PARASITIC  DISEASES. 

(c)  Entry:  By    mouth,    through  water  principally; 

less  often  in  ice,  milk,  and  other  foods;  in 
some  localities  oysters  are  especially  dan- 
gerous when  eaten  raw. 

(d)  Exit:  Discharges  from  bowels;  urine;  sputum; 

suppurative  complications;  skin;  in  rose- 
spots;  sometimes  in  vomit. 

(e)  Contracted:  The  specific  bacillus  must  get  into 

the  mouth  and  be  swallowed;  great  care 
must  be  exercised  by  those  in  attendance 
upon  typhoid  fever  patients  not  to  contam- 
inate their  foods,  or  the  foods  of  others. 

(f)  Disinfection:  The  bacillus  is  killed  immediately 

by  boiling  water  or  steam;  disinfect  the 
sputum,  the  stools,  discharges  from  the 
bowels,  urine,  linens,  eating-utensils,  etc., 
by  boiling,  or  by  5  per  cent  carbolic  acid, 
5  per  cent  formalin,  2  per  cent  tricresol, 
and  let  stand  one  hour;  bichloride  of  mer- 
cury (i-iooo)  may  be  used  to  disinfect  the 
urine.  When  convalescence  established, 
wash  out  bladder  once  daily  for  several 
days  with  bichloride  of  mercury  (1-20,- 
000),  or  give  urotropin  30  to  60  gr. 
daily  for  the  same  length  of  time;  all  dis- 
charges should  be  received  in  vessels  con- 
taining a  small  quantity  of  one  of  the  dis- 
infecting solutions,  after  which  the  balance 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.    211 

is  added  in  sufficient  quantity  to  make  up 
the  strength  recommended, 
(g)  Prophylaxis :  Wherever  human  excrement  is  used 
as    fertihzer,    eat   nothing   raw;    boil   all 
water  whether  used  for  drinking  purposes 
or    for    dish-washing,   unless   the   water- 
supply  is  above  suspicion;  boil  the  milk 
and  water  whenever  typhoid  prevails,  and 
use  no  ice  in  water  for  drinking  purposes; 
-screen  house  against  flies. 
The  essential  thing  in  prophylaxis  in  typhoid  fever, 
in    fact,  in  all  communicable  diseases,   is  to  see  to 
thorough  disinfection  of  all  infectious  discharges  in  the 
sick-room.     If  the  latter  were  done,  epidemics  of  com- 
municable diseases  could  easily  be  controlled.    The  fol- 
lowing directions,  as  given  by  Prof.  Osier,  are  the  pre- 
cautions  followed  in  the  Johns  Hopkins  Hospital  to 
guard  against  the  spread  of  typhoid  fever:     "Dishes 
must  be  isolated,  washed,  and  dried  separately,  and 
boiled  daily.     Thermometers  must  be  isolated,  kept 
in  bichloride  of  mercury  (i-iooo),  which  must  be  re- 
newed daily.     Linen,  when  soiled,  must  be  soaked  in 
carbolic  acid  (1-20),  for  two  hours  before  sending  to 
the  laundry.     Stools  must  be  thoroughly  mixed  with 
an  equal  amount  of  milk  of  lime,  and  allowed  to  stand 
one  hour.     Urine  must  be  mixed  with  an  equal  amount 
of  carbolic  (1-20),  and  allowed  to  stand  one  hour.     Bed- 
pans and  urinals  must  be  isolated  and  scalded  after 


212       INFECTIOUS  AND  PARASITIC  DISEASES. 

each  time  of  using.  Syringes  and  rectal  tubes  must  be 
isolated  and  the  latter  boiled  after  using.  Tubs  should 
be  scrubbed  daily  and  soaked  in  carbolic  as  the  linen 
is.  Hands  must  be  scrubbed  and  disinfected  after  giv- 
ing tubs  or  working  over  typhoid  fever  patients. 
Blankets,  mattresses,  and  pillows  must  be  sterilized 
after  use,  in  the  steam  sterilizer." 

Whooping-cough  (Pertussis). 

(a)  Cause:  Unknown. 

(b)  Localization:  Respiratory  tract. 

(c)  Entry:  Nose  and  mouth  through  air. 

(d)  Exit:  Secretions  from  nose  and  mouth. 

(e)  Contracted:  From  the  sick,  or  from  room,  hand- 

kerchief, etc.,  infected  by  same. 

(f)  Disinfection:  As    cause    not    known,    no    data. 

However,  boiling  water  or  steam,  and  the 
usual  strengths  of  the  chemical  disinfec- 
tants are  recommended.  Fumigate  with 
sulphur  or  formaldehyde. 

Yellow  Fever. 

(a)  Cause :  Not  known ;  mosquito  {stegomyia  fasciata) 

known  to  carry  the  virus. 

(b)  Localization:  Blood. 

(c)  Entry:  Bites  of  stegomyia  mosquitoes. 

(d)  Exit:  Through  bites  of  mosquitoes. 

(e)  Contracted :  Only  by  being  bitten  by  infected  mos- 

quitoes. 


MICRO-ORGANISMS  IN  VARIOUS  DISEASES.    213 

(f)  Disinfection:  Only  necessary  to  destroy  all  mos- 

quitoes in  sick-room  andihouse.  Sulphur 
or  pyrethrum  two  pounds  to  every  one  thoiT 
sand  cubic  feet  of  space,  exposure  two 
hours. 

(g)  Prophylaxis:  Protect   sick   from  bites  of   mos- 

quitoes; screen  houses,  use  mosquito  nets, 
and  destroy  mosquitoes  in  house  by  burn- 
ing sulphur  or  pyrethrum;  in  yellow  fever 
zones,  the  breeding  places  of  mosquitoes 
should  be  removed  or  drained;  persons 
while  out,  should  protect  themselves  from 
bites. 


CHAPTER  IX. 

DISINFECTION  AND  DISINFECTANTS  * 

The  purpose  of  disinfection  is  to  prevent  the  spread 
of  the  communicable  diseases.  In  its  apphcation  it 
aims  at  the  destruction  of  those  minute  forms  of  animal 
and  vegetable  life  which  prey  upon  both  man  and 
animals  and  cause  disease.  The  discovery  of  the  rela- 
tionship between  living  pathogenic  agents  and  disease; 
of  the  manner  in  which  these  same  agents  enter  and 
leave  the  body;  and  the  subsequent  determination  of 
reliable  methods  of  destroying  them,  marked  a  new 
epoch  in  the  history  of  medicine  in  so  far  that  disinfec- 
tion was  for  the  first  time  placed  upon  a  secure  founda- 
tion. As  a  result,  before  the  unseen  terrors  of  the  air 
and  water  we  no  longer  wring  our  hands  in  abject  and 
helpless  misery  while  thousands  of  our  fellow-beings 
are  smitten  by  disease!  Nor  do  we  inhumanly  flee 
from  those  afflicted,  leaving  them  not  only  to  the  mercy 
of  a  cruel  sickness,  but  also  to  those  beasts  among 

*For  most  of  the  data  in  this  chapter  and  much  in  the  preceding,  the 
author  has  drawn  freely  upon  Dr.  Rosenau's  "  Disinfection  and  Disin- 
fectants," an  incomparable  book  on  the  subject;  to  a  lesser  extent  upon 
Dr.  Sternberg's  "Lomb  Prize  Essay."  To  both  authors  he  gratefully 
acknowledges  his  indebtedness. 

214 


DISINFECTION  AND  DISINFECTANTS.  215 

humanity  who  see  in  calamities  only  opportunity  for 
hcense  and  profit!*  But  with  a  courage  born  of 
knowledge,  and  with  the  consciousness  of  power  which 
the  former  inspires,  we  fight  a  scourge  as  we  would  a 
ruthless  foe. 

The  weapons  used  against  infectious  diseases  are 
disinfectants  and  insecticides,  weapons  which  in  our 
own  generation  have  made  in  civilized  communities 
''plagues"  impossible.  Indeed,  were  it  not  for  the 
indifference  displayed  by  the  public  towards  sanitary 
science  in  not  providing  its  health  officers  with  ample 
resources  and  authority,  many  prevailing  infectious 
diseases,  such  as  tuberculosis,  typhoid  fever,  etc.,  would 
be  far  less  common,  and  would  year  by  year  claim  fewer 
victims,  until  they  too  would  in  time  come  to  be  spoken 
of  as  belonging  to  the  horrors  of  another  age. 

Often,  in  omitting  the  enforcement  of  sanitary 
measures,  physicians  and  nurses  seem  callous  to  the 
public  weal,  a  negligence  due  no  doubt  to  lack  of 
encouragement  from  the  patient's  family.  Yet  who 
are  in  better  positions  to  dam  at  their  source  the  springs 
of  disease  ?  In  every  infection  the  patient  is  an  incuba- 
tor, as  it  were,  for  pathogenic  microbes,  which  leave 
his  body  by  definite  channels  in  the  excretions  and 
secretions.  If  these  discharges  are  not  immediately 
made  innocuous,  there  is  the  probability  that  the  infec- 
tion will  be  spread.  The  task  of  disinfecting  any 
♦See  Walter  Reed  and  Yellow  Fever,  by  H.  A.  Kelly. 


2i6       INFECTIOUS  AND  PARASITIC  DISEASES. 

dangerous  discharge  at  the  bed-side  is  comparatively 
easy,  and  one  which  is  properly  a  duty  that  the  phys- 
ician should  direct,  and  which  the  nurse  or  family  should 
perform ;  and  were  this  duty,  which  is  one  to  humanity, 
always  conscientiously  discharged,  foods  and  drinks 
would  not  be  polluted  in  the  manner  described  in  pre- 
vious pages. 

The  importance  of  careful  disinfection  in  the  sick- 
room of  all  infectious  secretions  and  excretions,  of  bed- 
linen,  towels,  eating-utensils,  flat  surfaces,  etc.,  is 
quite  well  understood  by  the  public  generally,  and  is 
treated  at  length  in  text-books  familiar  to  both  phys- 
icians and  nurses.  Nor  do  the  descriptions  of  the 
various  disinfectants  and  their  use  differ  so  greatly  as  to 
require  special  mention.  The  following  brief  outline 
is  intended  solely  to  call  attention  to  the  most  efficient 
disinfectants,  and  to  the  strengths  of  the  chemical 
disinfecting  solutions  commonly  employed. 

Heat,  as  has  been  stated  elsewhere,  is  the 
Heat.  most  reliable  disinfectant  known.  Burn- 
ing, or  heating  objects  to  incandescence, 
renders  them  sterile.  However,  this  kind  of  disinfec- 
tion, it  is  obvious,  is  seldom  practicable,  and  we  must 
fall  back  upon  lower  temperatures.  Either  dry  or 
moist  heat  is  then  available.  Other  things  equal,  moist 
heat  is  a  far  more  efficient  destroyer  of  germ  life  than 
dry  heat,  because  it  has  greater  powers  of  penetration. 
Boiling  tubercle  bacilli  in  water  (212°  F.,  100°  C.)  for  ten 


DISINFECTION  AND  DISINFECTANTS.  217 

minutes  kills  them,  whereas  they  can  resist  a  dry  heat 
of  212°  F.  for  several  hours.  More  efficient  than  boiling 
is  live  steam,  especially  if  it  is  used  under  a  pressure  of 
from  one  to  three  atmospheres.  Special  apparatuses 
called  auto-claves,  are  used  for  this  purpose,  and  all 
important  sanitary  stations  possess  such  an  equip- 
ment. 

The  advantages  of  using  an  apparatus  in  which  steam 
under  pressure  can  be  employed  are  three-fold :  (i)  The 
penetrating  power  of  the  steam  is  increased;  (2)  since 
the  temperature  of  steam  rises  with  the  pressure,  its 
germicidal  power  is  accordingly  enhanced ;  (3)  on  account 
of  the  higher  temperature  and  greater  penetration,  the 
time  required  for  disinfection  is  greatly  diminished. 
As  a  matter  of  fact,  the  bulkiness  of  some  articles,  such 
as  mattresses,  bales  of  rags,  etc.,  practically  precludes 
disinfection  without  the  use  of  auto-claves  or  especially 
devised  disinfecting  chambers. 

Besides  steam,  formaldehyde  alone,  or  in  combination 
with  steam,  is  used  under  pressure  for  disinfection. 
Applied  together  in  this  way  the  two  are  more  quickly 
germicidal  than  either  gas  used  alone. 

Bacteria  differ  in  regard  to  the  temperature  required 
to  kill  them.  Almost  all  the  vegetative  forms  are  killed 
at  a  temperature  of  (60°  C,  140°  F.)  if  applied  for  ten 
minutes,  and  boiling  (100°  C,  212°  F.)  destroys  the  same 
at  once.  An  exception  to  this  rule,  as  we  have  else- 
where pointed   out,   is   the   tubercle  bacillus,   which, 


2i8       INFECTIOUS  AND  PARASITIC  DISEASES. 

although  only  occurring  in  a  vegetative  form,  can  with- 
stand the  temperature  of  boiling  water  (212°  F.,  100°  C.) 
for  ten  minutes.  In  practical  work,  boiling,  where 
possible,  is  resorted  to  for  all  vegetative  forms  of  bacteria, 
the  length  of  time  depending  upon  the  mass  of  material 
to  be  disinfected. 

Spores  of  bacteria  are  quite  difficult  to  kill.  Where 
the  apparatus  is  at  hand,  steam  under  a  pressure  of 
from  twenty  to  twenty-five  pounds  (temperature  230°  F., 
105°  C. — 240°  F.,  115.5°  C.)  is  used.  If  steam  under 
pressure  is  not  available,  boiling  for  an  hour  in  a  closed 


Fig.  26. — The  Pot  Method  of  Burning  Sulphur.     (Rosenau.) 

vessel  is  a  safe  rule.  Fortunately,  none  of  the  epidemic 
diseases  is  caused  by  a  spore-forming  microbe,  a  fact 
which  lightens  greatly  the  burden  and  responsibility 
imposed  upon  the  disinfector. 

Two  gaseous  disinfectants  are  in  common 
Gaseous       ^^^   throughout  the  world,  formaldehyde 
and  sulphur  dioxide.     Of  these,  formal- 
dehyde approaches  more  nearly  our  concep- 
tion of  an  ideal  disinfectant  than  does  sulphur  dioxide 


DISINFECTION  AND  DISINFECTANTS.  219 

or  any  other.  Compared  with  sulphur  dioxide,  formal- 
dehyde has  these  distinct  advantages,  namely,  it  is  non- 
poisonous,  is  a  true  deodorant,  and  does  not  attack 
metals,  colors,  or  fabrics.  On  the  other  hand,  it  does 
not  destroy  vermin,  as  does  sulphur,  a  disadvantage 
that  is  disappointing  in  the  light  of  what  recent  investi- 
gations have  taught  us  of  the  highly  important  part 
which  various  insects  play  in  the  conveyance  of  disease. 
To  obtain  the  best  results  with  both  formaldehyde  and 
sulphur  requires  a  full  knowledge  of  the  conditions 
under  which  they  are  generated,  of  the  apparatuses  used 
in  disinfection,  and  of  such  concomitant  arrangements 
of  rooms,  buildings,  conditions  of  temperature  and 
moisture,  etc.,  as  are  necessary.  It  is  not  the  intent  of 
this  chapter,  however,  to  enter  into  the  subject  of 
disinfection  so  extensively  as  such  a  description  would 
entail. 

Liquid     disinfectants    are    unequivocally 
Chemical      superior  to  gaseous  ones  if  direct  contact 

DiSINFEC-         ,  ,   .  .  .  .    .  c  ^-i 

by  washmg,  immersion,  or  mixing,  01  the 

TANTS  r  .  .  1 

(liquid)  disinfectant  and  infectious  matter  can  be 
accomplished.  Gases  cannot  be  depended 
on  for  more  than  surface  disinfection,  a  fact  which 
restricts  their  use  to  the  inaccessible  parts  of  rooms, 
buildings,  ships,  etc.,  and  to  works  of  art,  e.g.,  paintings, 
and  fine  fabrics. 

The  resistance  of  infectious  agents  to  chemical  dis- 
infectants is  subject  to  the  same  variations  as  their 


220       INFECTIOUS  AND  PARASITIC  DISEASES. 

resistance  to  heat.  Such  vegetative  forms  of  bacteria  as 
are  more  resistant  to  heat,  are  more  resistant  to  chem- 
icals ;  and  the  sporulating  forms  are  even  more  difhcult 
to  kill  with  chemicals  than  with  steam  under  pressure. 
Chemical  disinfectants  vary  greatly  in  the  strength  of 
each  required  to  be  efficient,  and  their  disinfecting 
powers  also  vary  with  the  material  to  be  disinfected. 
Very  powerful  disinfectants  may  fail  to  act  on  account 
of  chemical  union  taking  place  between  them  and  the 
material  in  which  the  infectious  agents  are  contained. 
Thus  both  bichloride  of  mercury  and  carbolic  acid 
lose  much  of  their  disinfecting  qualities  when  added  to 
albuminous  material,  on  account  of  the  formation  of  an 
insoluble  albuminate  which  is  inert.  Furthermore,  if 
one  of  these  substances  be  used  in  excess  in  the  belief 
that  the  above  defect  may  be  overcome,  the  end  is 
just  as  likely  not  to  be  realized,  because  this  insoluble 
combination  surrounds  the  infectious  agents  and  pre- 
vents contact  between  them  and  the  disinfectants. 
In  instances  of  this  kind  either  the  chloride  of  lime,  the 
cresols,  or  formalin  are  to  be  preferred.  Where  the 
medium  contains  much  organic  matter  or  filth,  even 
where  the  proper  disinfectant  is  used,  much  stronger 
solutions  than  commonly  employed  are  advisable.  An 
extremely  valuable  point  to  remember  in  applying  any 
of  the  chemical  disinfectants  is  that  the  disinfecting 
power  of  all  of  them  is  greatly  enhanced  if  they  are 
heated   with   the   material  to  be  disinfected;  and  the 


DISINFECTION  AND  DISINFECTANTS.  221 

higher  the  temperature,  the  more  is  their  disinfecting 
power  increased.  In  this  way  substances  of  feeble  dis- 
infecting powers  may  often  be  used  to  advantage.  The 
value  of  heating  a  disinfectant  is  well  illustrated  by  com- 
paring the  action  of  carbolic  acid  upon  the  anthrax  bacil- 
lus and  its  spores.  Anthrax  bacilli  are  killed  in  ten  sec- 
onds by  a  one  per  cent  solution  of  carbolic  acid,  yet  its 
spores  can  live  a  month  in  a  five  percent  solution.  But 
if  the  temperature  of  a  five  per  cent  solution  of  the  same 
acid  is  raised  to  75°  C.  (134.6°  F.),  they  are  killed  in 
three  minutes.  In  all  disinfection,  therefore,  hot  solu- 
tions should  be  used. 

DISINFECTING  SOLUTIONS. 

Perhaps  the  commonest  disinfectant  used 
Bichloride  is  bichloride  of  mercury  (corrosive  subli- 
OF  Mercury,  mate).     It  is  a  powerful  germicide,  even  in 

weak  solutions.  It  has  several  serious 
drawbacks,  however,  which  limit  its  usefulness ;  among 
these  is  the  fact  that  it  is  a  corrosive  poison;  that  its 
solutions  attack  practically  every  metal;  and  that  it 
unites  with  albuminous  matter.  For  the  last  reason  it  is 
not  to  be  used  as  a  disinfectant  for  the  disinfection  of 
sputum,  feces,  and  discharges  containing  albumin, 
such  as  pus.  For  washing  floors,  walls,  and  other  sur- 
faces, a  hot  solution  (i-iooo)  is  as  efficient  as  any  other 
disinfectant.  For  ordinary  purposes  the  i-iooo  solu- 
tion is  the  strength  employed.     This  can  be  prepared 


222       INFECTIOUS  AND  PARASITIC  DISEASES. 

from  the  tablets  when  a  small  quantity  is  desired,  or  in 
larger  quantity  by  taking 

Bichloride grs.  6iJ. 

Citric  acid  or  common  salt grs.  6iJ. 

Water gallon    i. 

The  i-iooo  solution  is  ample  for  the  destruction  of  all 
non-spore-bearing  bacteria  at  ordinary  temperatures 
in  one-half  hour.  For  spores,  stronger  solutions  (1-500) , 
and  a  longer  exposure  (one  hour),  are  advisable.  As  a 
disinfectant  for  the  hands  in  surgical  work,  and  as  a 
moist  dressing  in  various  inflammatory  conditions,  this 
solution  of  mercury  is  in  constant  use. 

Formalin  is  used  as  a  disinfectant  in  a  4  to 
Formalin.  5  per  cent  solution  of  the  40  per  cent  solu- 
tion of  the  gas  in  water.  Its  advantages  as 
a  disinfectant  are  many;  it  does  not  injure  most  fabrics; 
it  attacks  only  two  metals,  iron  and  steel,  and  these 
only  when  hot.  It  is  non-poisonous,  and  albuminous 
matter  does  not  interfere  with  its  action.  It  kills  spores. 
It  is  a  true  and  efficient  deodorant.  Urine,  feces, 
sputum,  and  all  albuminous  discharges,  are  quickly 
disinfected  and  deodorized  by  it. 

Carbolic  acid  is  a  useful  disinfectant  and 

Carbolic        is  with  reason  widely  used.     A  3  to  5  per 

Acid  (phenol),  cent    solution    (the    latter    1-20)    is    the 

strength    employed.     Since    it   does    not 

kill  spores,  it  should  not  be  used  after  anthrax,  tetanus, 


DISINFECTION  AND  DISINFECTANTS.  223 

malignant  oedema,  and  other  diseases  due  to  bacteria 
which  produce  spores.  Although  it  coagulates  albu- 
minous matter,  it  is  not  so  active  in  this  respect  as  bi- 
chloride of  mercury,  and  can  therefore  be  used  for  the 
disinfection  of  soiled  linens,  clothing,  and  also  for 
excreta.  It  is  well  to  remember  that  carbolic  acid  is  a 
powerful  corrosive  poison.  For  liquid  discharges  in 
cholera,  typhoid,  dysentery,  etc.,  a  5  per  cent  solution 
may  be  used,  when  twice  the  amount  of  carbolic  to 
material  is  advised.  The  mixture  should  be  allowed 
to  stand  four  hours. 

A  convenient  method  of  preparing  a  five  per  cent 
solution  (1-20)  is  as  follows: 

Carbolic  acid  (95  per  cent) ozs.  6i 

Water gallon  i 

Agitate  until  the  acid  is  thoroughly  dissolved  in  the  water. 

^  The  cresols  are  among  the  most  powerful 

I  'RT'~"'R'FROT 

and  valuable  disinfectants  known.  None 
of  them  are  as  poisonous  as  carbolic  acid  (phenol), 
nor  are  they  open  to  the  objection  that  albumin- 
ous material  interferes  with  their  action.  They  all 
kill  spores.  Tricresol  may  be  used  in  i  per  cent  solu- 
tion for  the  disinfection  of  infected  discharges  of  all 
kinds.  The  other  preparations  of  the  cresols,  solutol^ 
solveol,  lysol,  as  compared  to  tricresol,  have  a  reputation 
for  disinfecting  power  in  the  order  in  which  they  are 
named. 


224       INFECTIOUS  AND  PARASITIC  DISEASES. 

Lime  (quicklime),  as  such,  is  useful  for  the 
disinfection  of  cadavers  dead  of  infectious 
diseases.  For  this  purpose  twice  the  weight  of  the 
body  in  unslaked  lime  is  packed  about  the  cadaver, 
which  should  be  contained  in  a  tight  coffin.  Neither 
water  or  moisture  need  be  added. 

Which  is  prepared  from  the  slaked  lime 
Milk  of      (hydrate  of  lime,  calcium  hydrate)  by  add- 
LiME.        ing  one  part  by  weight  of  hydrate  of  lime  to 
eight  parts  of  water,  is  a  valuable  disin- 
fectant for  excreta. 

The  slaked  lime  used  in  the  preparation  should 
always  be  freshly  made  by  mixing  one  pint  of  water  to 
two  pounds  of  lime.  For  the  disinfection  of  stools, 
an  amount  of  milk  of  lime  equal  to  the  material  to  be 
disinfected  should  be  used,  and  the  mixture  be  allowed 
to  stand  two  hours.  Whitewash  is  slaked  lime  mixed 
with  water  to  the  consistency  of  a  thick  cream.  It  is  a 
valuable  means  of  disinfecting  the  walls  and  ceiling  of 
stables,  cellars,  and  other  rough  structures. 

Chlorinated  lime  is  best  adapted  for  the 
"Chloride  disinfection  of  excreta  and  sputum.  It  is 
OF  Lime."  both  deodorant  and  disinfectant.  For  dis- 
infecting purposes  dissolve  eight  ounces  of 
the  chloride  of  lime  in  a  gallon  of  water  (Sternberg). 
This  solution  should  be  placed  in  the  vessel  before  it 
receives  the  discharge.  From  one  to  two  quarts  are 
used  in  the  case  of  cholera  or  typhoid  stools.    After 


DISINFECTION  AND  DISINFECTANTS.  225 

thorough  agitation,  the  mixture  is  allowed  to  stand 
from  one-half  to  one  hour.  For  sputum,  an  amount 
equal  to  the  volume  of  the  sputum  should  be  added,  or 
the  sputum  cup  should  be  filled  about  one-half  with  the 
solution  before  use.  Chlorinated  lime  cannot  be  used 
for  the  disinfection  of  fabrics  or  colored  goods,  since  it 
bleaches  and  attacks  the  fabric  directly.  The  chlorin- 
ated lime  used  in  the  preparation  of  disinfecting  solu- 
tions must  have  been  contained  in  an  air-tight  receptacle, 
otherwise  from  exposure  to  the  air  much  of  its  disin- 
fecting powers  are  lost.  It  has  about  the  same  germi- 
cidal value  as  milk  of  lime. 


15 


CHAPTER  X. 

THE  COLLECTION  AND  EXAMINATION  OF 
SECRETIONS  AND  EXCRETIONS. 

This  chapter  in  introduced  as  an  aid  in  the  exami- 
nation and  collection  of  specimens  of  the  various  excre- 
tions, in  preserving  them  from  deterioration,  and  in 
describing  them  in  simple  terms  according  to  profes- 
sional custom.  Attention  is  directed  only  to  such  points 
as  may  be  of  value  either  to  the  observer,  or  to  another 
by  whom  the  specimens  are  to  be  examined  and  their 
significance  interpreted. 

From  many  standpoints,  the  sputum,  in 
Sputum,     disease,  possesses  very  great  importance. 

Its  bulk  is  made  up  of  pathological  secre- 
tions, abnormal  cellular  elements,  occasionally  tissues 
and  rarely  stones,  all  of  which  are  of  great  diagnostic 
significance ;  at  the  same  time,  it  is  the  vehicle  in  which 
the  pathogenic  agents  of  many  diseases,  both  local  and 
general,  make  their  exit  from  the  body.  From  a  mere 
visual  examination,  the  trained  observer  can  detect 
the  presence  of  features  characteristic  of  certain  dis- 
eases, and  abnormal  ingredients  that  are  suggestive  of 
disorders  of  certain  organs;  while  with  the  microscope 

226 


SECRETIONS  AND  EXCRETIONS.  227 

he  can  observe  the  presence  of  bacteria,  animal  para- 
sites or  their  eggs,  and  the  various  other  constituents 
invisible  to  the  unaided  eye. 

Attention  should  always  be  given  to  the 
Amount,      amount   of    sputum   expectorated    in   the 

twenty-four  hours,  since  only  in  this  way 
can  an  increase  or  decrease  be  definitely  determined. 
A  daily  record  should  be  kept  of  the  quantity,  other- 
wise in  the  rush  of  other  work  valuable  information 
may  be  lost.  Especially  important  is  a  knowledge  of  the 
amount  of  expectoration  in  case  of  haemorrhage,  or  of  a 
sudden  large  increase,  as  may  occur  when  an  hepatic 
abscess  ruptures  into  the  lungs.  The  twenty-four 
hours'  quantity  should  be  measured  for  the  reason  that 
many  patients  (e.g.,  pulmonary  tuberculosis,  bron- 
chiestasis)  expectorate  chiefly  only  during  one  or  two 
hours  in  the  twenty-four,  so  that  if  the  amount  expelled 
at  this  time  is  not  taken  into  account,  a  report  of  a  scanty 
expectoration  might  be  made. 

Consistence  of  a  sputum  is  another  charac- 
CoNsisTENCE.  tcristic  of  importance;  it  may  be  thin  and 

watery  (serous),  or  so  heavy  and  tenacious 
that  the  vessel  may  be  inverted  without  spilling  its  con- 
tents (mucoid).  Mucoid  sputum  is  seen  most  charac- 
teristically during  the  stationary  period  of  pneumonia. 
Between  these  two  extremes  there  may  be  various  de- 
grees of  consistency,  or  the  sputum  may  consist  of  both 
elements  distinctly  discernible  (muco-serous).     Thus, 


228       INFECTIOUS  AND  PARASITIC  DISEASES. 

in  pulmonary  tuberculosis,  when  the  sputum-cup  has 
stood  awhile,  the  contents  are  seen  to  consist  of  an  upper 
watery  layer,  and  a  lower  tenacious  mass  which,  when 
shaken,  is  seen  to  be  made  up  of  round,  coin-like  partic- 
les. This  is  the  so-called  mummular  sputum  which  is 
characteristic  of  the  second  and  third  stages  of  consump- 
tion. 

Worth  remembering  also  is  the  fact  that  on  standing 
twenty-four  hours  or  longer  in  a  warm  room,  a  tenacious 
sputum  may  become  liquefied  through  solution  of  its 
mucus  by  ferments. 

Much  valuable  information  may  be  derived 
Color.       from  the  color  of  a  sputum.     Sputum  may 

vary  from  the  clear  glairy  appearance  of 
normal  saliva,  to  grey,  yellow,  green,  red,  brown,  and 
even  black.  A  greenish  or  yellow  color  indicates  either 
pus  (purulent),  or  bile  (bilious);  a  red  color,  blood  (san- 
guineous); a  brown  or  chocolate  color,  liver  abscess; 
and  black,  carbon,  a  condition  resulting  from  the  inhala- 
tion of  carbon  particles  as  is  practised  by  smokers  for 
pleasure  or  by  miners  from  necessity. 

If  there  is  anything  unusual  to  the  odor  of  a 
Odor.       sputum,  it  should  be  noted.     Most  sputa 

are  practically  odorless.  However,  under 
certain  circumstances,  e.g.,  putrid  bronchitis,  the  other 
extreme  is  presented,  and  the  offensiveness  of  the 
expectoration  beggars  description.  In  pulmonary  tu- 
berculosis the  sputum  has  a  sweetish  odor. 


SECRETIONS  AND  EXCRETIONS.  229 

In  describing  a  sputum  a  single  predomi- 
nating characteristic  is  selected.     Thus  as 

D  ESCRIPTION 

c,  types  we  have  the  mucoid,  the  purulent, 

OF  A  Sputum.     -^  ^  '  r  ' 

the  serous,  and  the  sanguineous.     Where 
two  or  more  elements  are  plainly  mingled, 
such  terms  as  muco-purulent,  muco-serous,  sero-san- 
guineous,  and  sanguino-mucopurulent,  are  used  to  de- 
scribe it. 

Sputum  is  most  frequently  examined  for  the  tubercle 
bacillus,  and  where  it  is  to  be  submitted  to  an  expert 
with  this  object  in  view,  the  following  directions  should 
be  observed :  "Collect  the  sputum  in  a  clean  one  or  two- 
ounce  bottle  with  a  wide  mouth  and  a  water-tight  stop- 
per. The  bottle  should  be  labeled  with  the  name  of  the 
patient.  The  sputum  coughed  up  in  the  early  morn- 
ing is  to  be  preferred.  If  the  expectoration  be  scanty, 
the  entire  amount  coughed  up  in  the  twenty-four  hours 
should  be  collected.  Care  should  be  taken  that  the  con- 
tents of  the  stomach,  food,  etc.,  are  not  ejected  during 
the  act  of  coughing,  and  collected  instead  of  pulmonary 
sputum.  Purulent,  cheesy,  and  muco-purulent  sputa 
most  frequently  contain  tubercle  bacilli;  pure  mucus, 
blood,  or  saliva  do  not  as  a  rule  contain  them.  When 
haemorrhage  has  occurred,  if  possible  some  purulent, 
cheesy,  or  muco-purulent  sputum  should  be  collected 
for  examination.  The  sputum  should  be  forwarded  in 
as  fresh  a  condition  as  possible." 


230       INFECTIOUS  AND  PARASITIC  DISEASES. 

In  suspected  diphtheria,  for  the  purpose 
Diphtheritic  of  diagnosis,  and  after  recovery  from  diph- 
CuLTUREs.       theria,  before  raising  the  quarantine,  to 

determine  the  presence  or  absence  of  the 
specific  bacillus,  it  is  compulsory  in  many  cities  that  a 
specimen  be  taken  from  the  patient's  throat  and  sent  to 
the  municipal  laboratory  for  examination.  For  this  pur- 
pose a  special  outfit  is  furnished  consisting  of  two  glass 
tubes,  one,  containing  a  sterile  swab,  the  other,  a  cream 
or  chocolate  colored  jelly  which  fills  about  one- third  of 
the  tube.  The  material  in  the  second  tube  is  blood- 
serum  which  has  been  solidified  in  a  slanting  position 
by  heat.  To  make  a  culture,  the  swab  is  first  smeared 
over  the  affected  area  in  the  throat,  and  then  immediately 
applied  to  the  slanting  surface  of  the  blood-serum.  The 
tubes  are  then  returned  to  the  laboratory  where  the  one 
containing  the  blood-serum  is  placed  in  a  warm  oven 
(37.5°  C. — 98.6°  F.)  for  from  twelve  to  eighteen  hours. 
A  stained  preparation  of  the  bacteria,  which  by  this 
time  have  developed  upon  the  blood-serum,  is  now  ex- 
amined with  a  microscope,  and  the  presence  or  absence 
of  diphtheria  bacilli  determined.  The  following  di- 
rections, taken  from  the  literature  of  the  Philadelphia 
Health  Department,  is  an  illustration  of  the  instruc- 
tions which  accompany  the  tubes: 

DIRECTIONS  FOR  MAKING  CULTURES. 
"The  patient  should  be  placed  in  a  good  light,  and, 
if  a  child,  properly  held.     In  cases  where  it  is  possible 


SECRETIONS  AND  EXCRETIONS.  231 

to  get  a  good  view  of  the  throat,  depress  the  tongue  and 
rub  the  cotton  swab  gently,  but  freely,  against  any 
visible  exudate,  revolving  the  wire  between  the  fingers, 
so  as  to  bring  all  portions  of  the  swab  in  contact  with  the 
mucous  membrane  or  exudate.  In  other  cases,  includ- 
ing those  in  which  the  exudate  is  confined  to  the  larynx, 
pass  the  swab  as  far  back  as  possible,  avoiding  the 
tongue,  and  rub  it  freely  as  described  above  against  the 
mucous  membrane  of  the  pharynx  and  tonsils.    With- 


FiG.  27. — Method  of  inoculating  culture  media.  (WUliams.) 

draw  the  cotton  plug  from  the  culture  tube,  holding 
it  so  that  the  portion  withdrawn  from  the  tube  does  not 
come  in  contact  with  the  fingers  or  with  any  other 
substance.  Insert  the  swab  and  rub  it  gently  but 
thoroughly  back  and  forth  over  the  entire  surface  of 
the  blood-serum.  Do  not  allow  the  swab  to  touch 
anything  except  the  throat  of  the  patient  and  the  sur- 
face of  the  serum.  Do  not  push  the  swab  into  the 
serum,  nor  break  the  surface  in  any  way.     Do  not  use 


232        INFECTIOUS  AND  PARASITIC  DISEASES. 


o 


tubes  in  which  the  serum  is  contaminated,  is  liquefied 
or  is  dried  up.  Then  replace  the  swab  in  its  own  tube, 
plug  both  tubes,  mark  the  culture  tube  with  the  name 
of  the  patient  for  identification,  and  return  both  tubes 
to  the  laboratory.  Unsatisfactory  cultures  usually 
result  from  failure  to  follow  carefully 
the  above  directions."  Caution:  In 
making  cultures,  to  insure  a  successful 
result,  no  antiseptic  must  have  been 
used  in  the  patient's  throat  for  an  hour 
preceding  the  taking  of  the  culture. 

In  croup,  a  membrane  is  often 
coughed  up,  which  it  is  sometimes  de- 
sirable to  have  examined  to  determine 
the  nature  of  the  infection,  i.e.,  whether 
diphtheria  is  present  or  not;  in  such 
cases  it  is  especially  important  that  the 
specimen  be  not  placed  in  any  preserv- 
ing fluid  or  disinfectant,  since  such 
solutions  destroy  the  very  agents  which 
it  is  aimed  to  find. 

Vomiting  is  a  feature  in 
Vomit.       local  diseases  of  the  stom- 
ach ;  in  affections  of  neigh- 
boring organs  (heart,  liver) ;  it  also  occurs  at  the  onset 
and   during   the   progress  of   the  infectious  diseases. 
The  points  to  be  observed  in  vomiting  are  the  time,  color, 
odor,  quantity,  and  ingredients. 


Fig.  28. — Needles 
used  for  inoculating 
media. 


SECRETIONS  AND  EXCRETIONS.  233 

The  time  of  vomiting  is  important,  espe- 
TiME.  cially  in  relation  to  meals.  It  should  be 
noticed  whether  vomiting  immediately  fol- 
lows the  ingestion  of  food,  or  is  delayed  some  minutes 
or  hours;  also  whether  it  apparently  results  from  the 
ingestion  of  some  particular  article  of  diet.  Vomiting 
may  be  frequent,  as  in  the  early  months  of  pregnancy, 
or  it  may  be  sporadic,  as  in  dilatation  of  the  stomach. 
Sudden,  unexpected,  vomiting  practically  always  marks 
the  onset  of  the  eruptive  fevers  in  children. 

Color  is  given  to  the  vomit  either  by  the 
Color.       foods   ingested,   or  by  foreign  or  patho- 
logical  constituents    such   as  bile,  blood, 
mucus,  etc. 

As  a  rule  the  vomit  is  green  or  golden  in 
Bile.         color  from  admixture  with  bile,  a  secre- 
tion which  is  always  present  in  intense  or 
continuous  vomiting. 

Red  vomit  usually  results  from  admixture 
Blood.  with  blood.  If  the  blood  has  not  been 
acted  upon  by  the  digestive  juices,  it  is 
easily  recognized ;  but  the  gastric  ferments  may  so  alter 
its  appearance  that  the  vomit  may  vary  from  a  deep- 
red  to  a  coffee  or  black  color.  Black  vomit,  it  will  be 
remembered,  is  a  characteristic  symptom  in  yellow 
fever.  Vomit  may  also  be  dark  from  the  presence  of 
stercoraceous  material  (feces).  Care  should  always 
be  taken  not  to  mistake  food  for  evidence  of  pathological 


234       INFECTIOUS  AND  PARASITIC  DISEASES. 

vomit.  The  writer  was  once  sent  the  red  vomit  of  a 
pregnant  woman  for  examination,  haemorrhage  being 
suspected.  The  red  color  was  due  to  nothing  more 
serious  than  ripe  tomatoes  which  anyone  might  have 
seen  had  they  looked  well. 

The  normal  odor  of  the  gastric  contents 
Odor.       is  acid.     In  disease,  it  may  be  "beefy" 

from  the  presence  of  blood ;  putrid  in  can- 
cer or  dilation;  ammoniacal  in  uraemia.  In  stercora- 
ceous  vomiting  it  has  the  characteristic  odor  of  the 
stools. 

Measure  or  gauge  as  accurately  as  pos- 
QuANTiTY.      sible  the  quantity  vomited.     The  normal 

stomach  has  a  capacity  of  three  pints,  an 
amount  which  may  be  increased  in  dilatation  to  three 
or  more  quarts.  The  quantity  vomited  also  furnishes 
important  information  as  to  the  absorptive  and  diges- 
tive powers  of  the  stomach,  especially  when  considered 
in  connection  with  the  amount  and  kind  of  food  in- 
gested. To  obtain  the  latter  data,  physicians  are  in  the 
habit  of  giving  a  measured  quantity  of  food  (test-meal), 
and  within  an  hour  withdrawing  it  with  a  stomach- 
tube  for  examination. 

Test-meals  are  given  either  in  the  morning 
Test-meals,    or  at  noon,  and,  depending  upon  the  time 

given,  are  called  respectively  test- breakfast 
or  test-dinner.  The  most  common  test-meal  is  the 
breakfast.    Two  breakfast  formulae  are  in  common  use. 


SECRETIONS  AND  EXCRETIONS.  235 

which  are  named  after  their  originators,  Ewald  and 

Boas. 

Test-break-  Consists  of  from  35  to  70  grams  (2  ounces) 

FAST  OF  of  wheat  bread,  and  of  300  to  400  cu.  cm. 

Ewald  AND     (ji  to   2   glasses)  of  water,  or  weak  tea 

Boas.  without  sugar. 

Consists  of  oatmeal  soup,  prepared  by 
Test-break-  boihng  down  to  500  cu.  cm.  (17  fluid 
fast  of  Boas,  ounces)  one  liter  (quart)  of  w^ater  to  which 

one  tablespoonful  of  rolled  oats  has  been 
added.    A  little  salt  may  be  added,  but  nothing  more. 

Soup  400  cu.  cm.  (2  glasses),  beefsteak 
Test-dinner  200  grams  (7  ounces),  wheat  bread  50 
OF  RiEGEL.      grams  (i|  ounces),  water  200  cu.  cm.  (i 

glass).  Finely  chopped  meat  may  be  sub- 
stituted for  the  beefsteak. 

Besides  the  contents  already  mentioned 
Ingredients,  above,   the   vomit   always   contains   more 

or  less  mucus  and  saliva.  Food  in  all 
stages  of  digestion  will  be  noticed,  and,  if  present,  the 
segments  (proglottides)  of  tape-worms,  the  adult  round 
worm  (ascaris  lumbricoides),  and  the  thread-like 
trichinae.  Foreign  indigestible  objects,  which  have 
been  swallowed,  may  be  discovered,  such  as  pins, 
needles,  whistles,  etc.  These  are  found  most  often  in 
the  vomit  of  children,  the  insane,  and  in  hysterical 
subjects.  In  the  last  class  of  patients  the  most  rigid 
surveillance  must  be  practised  to  prevent  deception. 


236       INFECTIOUS  AND  PARASITIC  DISEASES. 

From  an  examination  of  the  blood  alone, 
Blood  the  diagnosis  of  a  limited  number  of  dis- 

Specimens.  eases  can  often  be  made.  In  a  few,  as 
for  example  malaria,  the  agents  of  the  dis- 
ease can  be  detected  with  the  microscope  in  properly 
prepared  specimens;  in  others,  e.g.,  typhoid  fever, 
when  a  drop  of  blood  is  brought  in  contact  with  known 
typhoid  bacilli,  a  characteristic  phenomenon,  WidaVs 
reaction^  takes  place,  which  consists  in  a  clumping  or 
drawing  together  of  the  bacilli;  in  still  another  class  of 
diseases,  the  diagnosis  is  made  by  determining  the 
number  of  red  and  white  corpuscles  present  in  one 
cubic  centimeter  of  blood,  and  noting  in  what  respects 
their  number  and  appearance  differ  from  that  which  is 
normal.  In  cities  maintaining  municipal  labora- 
tories, outfits  for  the  collection  of  specimens  of  blood 
for  the  diagnosis  of  both  malaria  and  typhoid  fever  are 
supplied. 

This  outfit  for  typhoid  fever  consists  of 
Typhoid  either  a  slip  of  unglazed  paper,  a  glass 
Fever  slide,  or  a  metal  plate,  upon  which  the 
(Widal)  blood  is  to  be  collected,  and  a  needle  for 
Outfit.  puncturing  the  ear  or  finger.  These  with 
the  directions  for  taking  the  blood  are 
enclosed  in  an  envelope. 

The  directions  for  taking  the  blood-drop  on  paper 
are  as  follows: 

^'Thoroughly  cleanse  the  skin  of  the  patient's  finger- 


SECRETIONS  AND  EXCRETIONS. 


237 


tip  or  the  lobe  of  the  ear.  After  carefully  drying,  prick 
it  with  a  needle  previously  sterilized  by  heating  over  a 
lamp  or  gas  flame  and  allowed  to  cool.  Allow  five  or 
more  large  drops  of  blood  to  dry  on  the  inner  surface  of 
a  piece  of  paper.  Replace  the  folded  paper  in  the  en- 
velope, and  return  to  the  laboratory."  Where  a  glass 
slide  or  a  thin  sheet  of  metal  is  used  in  place  of  the 


Fig.  29. — Application  of  the  Serum-reaction  to  Typhoid  Bacilli.  (Williams.) 
A,  shows  the  distribution  of  the  bacilli  before  the  reaction.  B,  shows  clump- 
ing of  the  motionless  bacilli  after  mixture  with  the  serum  of  a  case  of  typhoid 
fever.   (Diagrammatic.) 

paper,  the  directions  for  the  collection  of  the  blood 
specimens  do  not  differ  materially  from  the  above. 

As  a  rule  the  Widal  reaction  is  not  given  by  the  blood 
in  typhoid  fever  before  the  sixth  or  seventh  day,  and 
sometimes  not  until  almost  the  end  of  the  sickness;  for 
this  reason  it  is  advisable  to  prepare  a  second  specimen 
of  the  blood  after  a  few  days  in  case  the  first  specimen 


238       INFECTIOUS  AND  PARASITIC  DISEASES. 

proves  negative.  In  about  five  per  cent  of  the  cases  the 
reaction  is  never  obtained  during  the  whole  course  of 
the  disease,  a  fact,  it  would  appear  from  recent  studies, 
due  to  the  presence,  as  causative  factor  in  the  disease, 
of  another  bacterium,  the  para-colon  bacillus.  Blood 
from  such  a  case  when  tested  with  a  para-colon  bacillus, 
gives  the  characteristic  reaction. 

For  the  detection  of  the  malarial  parasites 

Malaria,  either  glass  slides  or  cover-glasses  are  used, 
the  former  being  given  the  preference  by  the 
majority  of  municipal  laboratories.  The  directions  for 
preparing  specimens  of  blood  in  suspected  malarial 
fever  as  given  by  the  New  York  Health  Department, 
are  as  follows: 

"Wash  two  glass  slides  with  alcohol,  and  wipe  with 
a  soft,  clean  linen  cloth  (not  a  soiled  handkerchief) 
until  clean  and  shiny.  On  cold,  damp  days  the  slide 
should  be  warmed  over  a  flame.  After  cleaning,  the 
slides  must  be  held  by  the  sides  (FF  in  diagram),  and 
surfaces  and  ends  not  touched.  Clean  the  patient's 
ear-lobe  with  alcohol  and  prick  the  skin  with  a  sterile, 
surgical  needle  or  a  small  pointed  scalpel,  so  as  to  act- 
ually incise  the  capillaries.  The  blood  should  not  be 
squeezed  out,  but  should  flow  freely.  Wiping  off  the 
first  few  drops,  the  third  or  fourth  drop  should  be 
quickly  (before  it  gets  much  larger  than  a  pin  head) 
taken  up  on  the  edge  of  one  end  of  one  slide.  Place 
this  edge  on  the  surface  of  the  other  slide,  as  indicated 


SECRETIONS  AND  EXCRETIONS. 


239 


in  the  diagram,  and  as  soon  as  the  blood-drop  has 
spread  along  the  line  of  contact,  draw  the  upper  slide 
gently  along  the  surface  of  the  lower,  thus  spreading 
the  blood  in  a  thin  film.  Dry  this  by  waving  in  the  air. 
Do  not  heat.  Repeat  the  process,  using  the  edge  of 
the  prepared  slide  to  spread  the  blood  upon  the  other 
slide.  The  blood  should  be  taken  before  quinine  has 
been  administered,  as  quinine  quickly  expels  most  of  the 
malarial  parasites  of  this  latitude  from  the  capillary 
blood.     Under   such    circumstances    negative   reports 


Fig.  30. 

count  for  little  or  nothing.  The  blood  should  be  drawn 
just  hejore,  during^  or  just  after  the  supposed  malarial 
paroxysm,  as  the  parasite  is  present  in  the  capillaries 
in  much  greater  numbers  at  those  times." 

When  cover-glasses  are  preferred,  two  or  more  cover- 
glasses  are  cleansed  in  precisely  the  same  way  as 
described  for  slides.  A  small  drop  of  blood  is  caught  in 
the  center  of  one  cover-glass  by  bringing  the  latter  in 
contact  with  the  former.  Then  the  second  cover-glass 
is  allowed  to  fall  gently  upon  the  other.  If  the  glasses 
have  been  well  cleansed,  the  blood  will  immediately 


240       INFECTIOUS  AND  PARASITIC  DISEASES. 

spread  in  a  thin  layer  between  them,  when  they  are  at 
once  separated  by  gently  drawing  one  over  the  other 
in  the  same  plane,  i.e.,  parallel  to  the  other. 

If  an  examination  of  the  red  and  white 

Specimen  FOR  elements  of  the  blood  is  to  be  made,  blood 

oRPuscuLAR  ^^^^  ^^^  prepared  upon  slides  or  cover- 

EXAMINA-  ,  .1  1  -1       1    f 

glasses  m  the  same  way  as  described  for 


TION. 


malaria. 


Fig.  31. — Cover-glass  is  touched  to  summit  of  a  drop  of  blood  and 
then  allowed  to  fall  on  a  second  cover-glass,  margins  overlapping. 
Method  of  separating  cover-glasses.  (Clinical  Diagnosis,  Boston.) 


The  microscopical  examination  of  purulent 
Pus  AND  or  other  discharges  often  permits  of  the 
OTHER  immediate  discovery  of  the  agents  causing 

Discharges,  a  disease,  a  fact  which  may  be  of  incalcul- 
able benefit  to  the  patient,  and  a  sure  guide 
for  the  doctor.  This  is  the  case,  for  example,  in  puru- 
lent ophthalmia,  a  suppurative  conjunctivitis  most  fre- 
quently observed  in  the  new-born,  although  also  found 


SECRETIONS  AND  EXCRETIONS. 


241 


In  making 
of 


in  adults,  and  which  if  not  recognized  speedily  leads 
to  permanent  blindness.     Specimens  of  such  discharges 
are  collected  upon  slides 
or   cover-glasses    in    the 
same  way  as  described  for 
malaria,  care  being  exer- 
cised that  the  smears  are 
not  too  thick, 
smears   in  this   class 
cases,  it  is  safest,  on  ac- 
count of  the   danger  of 
self-infection,    to  use  an 

object  easily  destroyed,  as         Fig.  32.— Intra-ceUular  (a)  and  (b.,  c.) 
for  example  a  tooth-pick,     extra^cellular  gonococd.     (Casper.) 

which  is  then  burned. 

No  secretion  during  sickness  is  subject  to 
Urine.       closer  scrutiny  than  the  urine.     It  is  the 

chief  avenue  for  the  elimination  of  nitro- 
gen from  the  body,  as  well  as  for  other  substances  which, 
if  retained,  are  distinctly  harmful.  In  many  diseases  it 
is  the  channel  of  exit  for  the  specific  bacteria  from  the 
body.  Such  highly  significant  data  bearing  upon  a  pa- 
tient's illness  are  obtained  from  a  study  of  the  urine, 
that  the  precise  condition  of  this  secretion  is  always  as- 
certained. 

Normal  urine,  when  freshly  voided,  should 
Color.       be  perfectly  clear  or  faintly  cloudy.     Its 

color  is  variable,  verging  from  a  light  yellow 
16 


242        INFECTIOUS  AND  PARASITIC  DISEASES. 

or  straw,  to  a  brownish-red.  The  color  of  all  urines 
deepens  upon  standing,  while  at  the  same  time  a  cloud 
forms  which  gradually  sinks  to  the  bottom  of  the  vessel 
which  contains  it.  Urines  which  are  allowed  to  get 
chilled  are  often  quite  cloudy  or  opaque,  and  when  pre- 
senting this  appearance  are  sometimes  taken  to  indi- 
cate an  abnormality  in  the  secretion.  Opacity  from 
this  cause  is  quickly  dissipated  on  the  application  of 
heat. 

Pathological  urines  exhibit  the  same  variations  in 
shades  as  the  normal.  The  color  of  all  urines  is  sub- 
ject to  seasonal  variation,  being  pale  in  winter  and  dark 
in  summer.  A  pale  urine  simply  indicates  an  excess  of 
water.  The  color  of  urine  is  also  influenced  by  the 
food  ingested. 

Urines  are  described  as: 

(i)  Pale  or  straw  color. 

(2)  Amber. 

(3)  Reddish-yellow  or  red  (high  color). 

(4)  Reddish-brown  (dark  urine). 

Besides  these  shades  the  urine  may  be  green  from 
bile,  red  from  blood,  black  from  melanin,  blue  from 
indican  or  after  the  ingestion  of  methylene  blue,  yellow 
from  santonin  or  rheum,  and  milk-like  from  the  presence 
of  pus  or  chyle  (chyluria).  In  filariasis,  the  urine  may 
contain  both  chyle  and  blood,  a  condition  to  which  the 
name  hcematochyluria  has  been  given. 


SECRETIONS  AND  EXCRETIONS.  243 

Bile  imparts  to  urine  a  yellow  or  greenish- 
BiLE.         brown  color,  and  can  usually  be  detected 

at  once  upon  inspection.  If  a  urine  con- 
taining bile  be  shaken,  the  foam  which  collects  upon  the 
top  will  be  found  of  a  yellowish  or  greenish  hue  even 
when  these  colors  are  not  pronounced  in  the  body  of  the 
urine.  The  same  urine  when  filtered  also  leaves  a 
greenish  stain  upon  the  filter-paper. 

Five  to  ten  cubic  centimeters  of  urine  are 

placed  in  a  test-tube  and  treated  with  two 

^  to  three  cubic  centimeters  of  tincture  of 

FOR  Bile. 

iodine  (which  has  been  diluted  with  alcohol 

in  the  proportion  of  one  to  ten)  in  such 
manner  that  the  iodine  solution  forms  a  layer  above  the 
urine.  In  the  presence  of  bile,  a  distinct  emerald- 
green  ring  is  seen  at  the  zone  of  contact. 

Blood  gives  urine  a  color  which  may  vary 
Blood.      from   bright   red   to   dark   brown.     Such 

urine  turns  darker  upon  standing.  In 
cases  in  which  blood  is  voided,  it  is  important  that  the 
urine  of  a  single  micturition  be  passed  in  two  or  three 
portions.  A  person  voiding  urine  mixed  with  blood 
is  said  to  suffer  from  hceinaturia.  When  the  blood  is 
dissolved  in  the  urine,  i.e.,  the  haemoglobin  has  left  the 
corpuscles,  the  condition  is  called,  hcBmoglobinuria. 
Sometimes  it  is  difficult  to  distinguish  blood  from  bile  in 
urine,  as  both  may  present  the  same  appearance.  They 
can  usually  be  distinguished  by  dilution  with  water 


244       INFECTIOUS  AND  PARASITIC  DISEASES. 

which  acts  so  as  to  bring  the  red  color  of  the  blood  more 
prominently  into  view. 

Urine   containing  pus,   when   allowed   to 

Pus.        stand  a  short  time,  exhibits  a  heavy  white  or 

creamy  precipitate.     If  shaken  or  poured 

out,  it  is  seen  to  be  tenacious  or  stringy.     Pus  is  often 

associated  with  blood  in  the  urine. 

Salol    is    so    frequently    prescribed,    that 

Green      attention  is  directed  to  the  fact  that  urine 

Urine.      voided  by  a  patient  taking  it  becomes  green 

and  eventually  black  upon  standing. 

The  quantity  voided  in  the  twenty-four 

Quantity,    hours  is  subject  to  great  variations,  usually 

bearing  a  relation  to  the  quantity  of  fluids 

ingested.     Exercise,    sleep,    temperature,    atmospheric 

moisture,  all  influence  the  urinary  secretion. 

An  adult  ordinarily  voids  between  twelve  hundred 
and  fifteen  hundered  cubic  centimeters  (thirty-five  to 
fifty  ounces)  of  urine  in  the  twenty- four  hours.  Most 
individuals  do  not  void  urine  after  retiring;  and  if  this 
has  been  the  rule,  a  departure  from  this  habit  should  be 
viewed  with  suspicion. 

Polyuria  is  the  condition  in  which  unusually 
Polyuria,     large  amounts  of  urine  are  passed  in  the 
twenty-four  hours.     An  extreme  grade  of 
polyuria  is  common  in  diabetes;  and  in  that  form  in 
which  sugar  is  also  present  (diabetes  mellitus),  twenty- 
five  or  more  liters  (quarts)  is  not  very  unusual. 


SECRETIONS  AND  EXCRETIONS. 


245 


Oliguria  is  that  condition  in  which  amounts 
Oliguria,    of  urine  below   the   average   are  passed.' 

Usually  it  is  a  very  serious  symptom ;  how- 
ever, it  is  occasionally  seen  in  neurasthenics. 

The  odor  of  urine  is  of  slight  significance. 
Odor.       The  normal  odor  is  described  as  like  that 

of  ''bouillon/'  "oysters,"  or  ''new  hay." 
Uriniferous,  as  applied  to  urine,  describes  its  odor  after 
decomposition  has  taken  place.  Freshly  voided  urines 
which  are  uriniferous  are  pathological. 

The  specific  gravity  of  the  urine  is  deter- 
Specific  mined  with  an  instrument  called  a  urin- 
Gravity.     ometer.     With  the  urinometer  is  supplied 

a  cylindrical  vessel  which  is  to  hold  the 
urine  while  the  specific  gravity  is  be- 
ing taken.  To  determine  the  specific 
gravity  the  cylinder  is  nearly  filled 
with  urine,  when  the  urinometer  is 
slowly  introduced.  The  specific 
gravity  is  read  directly  from  the 
scale  at  the  upper  end  of  the  in- 
strument where  the  surface  of  the 
urine  meets  a  division  on  the  scale.     ^  ^.     ,      . 

Fig.  33. — Simple  Urin- 
A   sample    of    the  twenty-four  hours'    ometer  and  Accessories. 

output  should  be  employed.  ^^^ 

Normally  the  specific  gravity  varies  between  loio 
and  1025;  pathologically,  between  1002  and  1060. 
Urines  containing  albumin  have  their  specific  gravities 


246       INFECTIOUS  AND  PARASITIC  DISEASES. 

between  1005  and  loio;  those  containing  sugar,  between 
1030  and  1040.  To  be  sure,  these  hmits  are  often 
exceeded  or  diminished. 

The  reaction  of  normal  urine  is  acid, 
Reaction,  although  specimens  passed  at  different 
times  may  be  neutral.  The  reaction  of  a 
urine  is  obtained  by  wetting  pieces  of  filter-paper  which 
have  been  colored  red  or  blue  by  saturation  with  red  or 
blue  litmus.  If  a  urine  be  acid  it  will  impart  to  the  blue 
paper  a  red  color;  if  alkaline,  the  red  paper  will  be 
changed  to  blue.  Normal  urines  sometimes  alter  the 
color  of  both  papers  slightly;  such  urines  are  said  to  be 
amphoteric.    The  latter  is  of  no  significance. 

Albumin  in  urine  is  always  an  indication  of 

Albumin,      disease.     Tests  for  its  presence  should  be 

made  as  a  routine  procedure. 

To   determine   the   presence  of  albumin. 

Nitric  (i)  fill  a  test-tube  two- thirds  full  of  urine 

Acid  Test,    and  apply  gentle  heat  to  the  upper  surface 

until  it  begins  to  boil.    Now  add  a  few 

drops  of  concentrated  nitric  or  acetic  acid.     Should  the 

urine  remain  clear  it  is  free  from  albumin;  if  cloudy 

upon  boiling,  and  the  cloud  does  not  clear  up  upon  the 

addition  of  the  acid,  it  contains  albumin. 

(2)  Add  a  few  cubic  centimeters  of  con- 

CoNTACT      centrated  nitric  acid  to  a  test-tube  and. 

Test.  while   inclining  the  tube  at  an  angle  of 

about  forty-five  degrees,  with  a  pipette  let 


SECRETIONS  AND  EXCRETIONS.  247 

a  few  cubic  centimeters  of  urine  flow  down  the  sides  of 

the  tube  so  that  it  floats  upon  the  acid.    Hold  the  tube 

straight  and  to  the  hght,  when  if  albumin  be  present  a 

white  ring  will  be  seen  at  the  junction  of  the   two 

fluids. 

Caution :  Filter  the  urine  before  applying  any  test  for 

albumin. 

The  presence  of  sugar  in  urine  is  deter- 

^         mined  by  heatino;  a  few  cubic  centimeters 
Sugar  Test 

of  Hain's  solution  in  a  test-tube,  and  then 

immediately,  upon  removal  from  the  flame, 
adding  a  few  drops  of  the  suspected  urine.  If  sugar 
is  present  the  blue  color  of  the  solution  will  be  changed  to 
a  canary  or  reddish  yellow.  Always  boil  and  filter 
urines  containing  albumin  before  applying  the  test  for 
sugar. 

Bacteria,  and  the  eggs  of  animal  parasites. 
Foreign  are  also  at  various  times  eliminated  in  the 
Substances,    urine.     But  as  this  phase  of  the  subject 

is  treated  in  detail  in  another  chapter, 
reference  is  made  to  it  here  for  the  sake  of  completeness 
only. 

At  times,  however,  other  things  are  voided  in  the  urine 
which  should  be  spoken  of  in  this  place.  Reference 
is  made  to  gravel  and  stones  from  the  kidneys  or  blad- 
der, hair  from  dermoid  cysts,  fecal  matter  (in  vesico- 
rectal fistula),  etc.  In  hysterical  subjects  and  the 
insane,  hairs,  beans,  fish-bones,  etc.,  may  be  actually 


248       INFECTIOUS  AND  PARASITIC  DISEASES. 

voided,  or  be  passed  off  on  the  physician  as  having 
been  voided.  Where  the  objects  are  really  passed 
in  the  urine,  they  are  introduced  into  the  urethra  or 
bladder  before  micturition.  Hair,  however,  may  be 
passed  in  the  urine  in  cases  of  dermoid  cysts  of  the 
bladder. 

When  preparing  a  specimen  for  examina- 
CoLLECTioN  tion,  a  portion  of  the  full  twenty-four  hours' 
OF  Specimen,   secretion    should    be    chosen.     Although 

this  does  not  always  furnish  the  most 
satisfactory  sample,  it  is  the  safest  rule  to  follow  in  the 
absence  of  specific  instructions.  In  one  form  of  Bright's 
disease,  for  example,  albumin  is  present  only  an  hour 
or  two  after  meals,  and  then  in  very  small  amounts, 
so  that  the  examination  of  a  twenty-four  hours'  mixture 
might  not  reveal  its  presence.  In  like  manner,  in 
diseases  of  the  genito-urinary  organs,  the  twenty-four 
hours'  secretion  does  not  give  as  much  information  as 
one  or  several  specimens  collected  during  a  single  act 
of  micturition;  and  in  affections  of  these  parts  the 
patient  is  directed  to  divide  his  urine  while  voiding  it 
into  two  or  three  portions.  If  possible  always  send 
at  least  four  ounces  of  urine  for  examination.  Unless 
the  urine  can  be  examined  in  a  few  hours,  keep  it  in  a 
cool  place;  or  add  to  it  gr.  v  of  boracic  acid,  or  one 
dram  of  chloroform,  to  every  four  ounces  of  urine. 
Formalin,  m.  i  to  four  ounces,  is  also  an  excellent 
preservative. 


SECRETIONS  AND  EXCRETIONS.  249 

The  observations  to  be  made  of  the  stools 
Feces.       include  the  number,  amount,  consistence, 

form,  color,  and  odor  of  the  movements,  and 
further,  the  presence  or  absence  of  mucus,  blood,  pus,  gas 
bubbles  (which  denote  fermentation),  animal  parasites 
(e.g.,  worms  or  segments  of  same),  foreign  bodies  (e.g., 
pins,  coins,  etc.),  gall-stones,  and  undigested  food 
particles.  When  blood,  pus  or  mucus  is  discovered, 
its  relation  to  the  rest  of  the  movement  should  be  noted, 
that  is  to  say,  whether  the  same  is  mixed  with  the 
stool,  clings  to  it,  or  is  passed  separately  before  or  after. 

Normally  the  number  of  stools  in  different  in- 
NuMBER.     dividuals  is  subject  to  great  variations,  so  that 

it  is  impossible  to  fix  a  standard  which  will  ap- 
ply to  every  one.  Thus,  while  it  is  usual  for  the  majority 
of  persons  to  have  at  least  one  movement  in  the  twenty- 
four  hours,  it  is  not  uncommon  to  find  some  who  exceed 
this  number  by  one  or  two  stools,  and  still  others  for 
whom  one  stool  in  two  or  three  days  is  apparently 
normal.  Wide  variations  in  the  number  of  stools  is 
compatible  with  good  health.  For  the  average  person, 
however,  at  least  one  movement  daily  is  requisite;  less 
than  this  number  constitutes  constipation,  and  more, 
several  loose  movements,  diarrhoea.  Both  constipation 
and  diarrhoea  are  important  symptoms  not  only  in 
diseases  of  the  alimentary  tract,  but  of  systemic  affec- 
tions as  well,  and  the  history  of  no  case  is  complete 
without  a  record  of  the  state  of  the  bowels. 


250       INFECTIOUS  AND  PARASITIC  DISEASES. 

The  amount  of  fecal  matter  does  not  vary 
Amount,      so  much  as  the   number  of  stools,  since 

the  greater  the  number,  the  smaller  the 
individual  movements,  and  vice  versa.  The  size  of  the 
stool  bears  a  relation  to  the  kinds  of  food  eaten,  a  diet 
rich  in  vegetables  and  starchy  foods  leaving  a  much 
larger  residue  than  one  rich  in  animal  proteids. 

The  consistence  of  a  stool  depends  upon 
Consistence,  the  amount  of  water  present.     In  health 

the  food  determines  the  amount  of  the 
latter,  being  greater  with  a  vegetable  than  a  proteid 
diet. 

Stools  are  described  in  regard  to  their  consistency  as 
thin,  mushy,  or  watery;  and  hard  and  dry  (scybalous). 

The  color  of  a  stool  varies  with  the  charac- 
CoLOR.      ter  of  the  food  ingested.     It  may  be  quite 

light,  as  in  a  person  restricted  to  a  milk 
diet ;  green  from  green  vegetables ;  and  black  from  a  diet 
containing  an  abundance  of  rare  or  raw  meat.  All 
stools  turn  darker  upon  exposure  to  light.  In  disease 
the  stools  may  be  golden,  yellowish-green,  or  green, 
from  bile;  pasty  and  greyish  or  white,  in  diseases 
of  the  liver  or  bile  passages;  red,  brownish-red,  coffee- 
colored,  or  black  (tarry)  from  blood;  dark  blue  from  the 
administration  of  methylene  blue.  Calomel  turns  the 
stool  green.  The  number  of  stools  also  has  a  bearing 
upon  their  color,  the  larger  the  number,  the  lighter  the 
color  of  the  individual  movements. 


SECRETIONS  AND  EXCRETIONS.  251 

Examinations  of  the  stools  are  frequently 

advisable  for  the  purpose  of  discovering, 

if  possible,  gall-stones,  animal  parasites, 

and  eggs  of  parasites. 

If  gall-stones,  worms,  or  any  other  abnor- 

T-       mal  constituent  is  to  be  sought  in  the  stools, 
STONES,  Etc.     ,      ^  „      .  ,         •        i   •     1 1 

the  foUowmg  procedure  is  advisable: 

(i)  Have  stools  for  twenty-four  or  forty-eight  hours 

passed  into  a  large  vessel. 

(2)  Mix  each  stool  with  about  a  gallon  of  water  and 
stir  thoroughly;  let  stand  for  one-half  hour  and  then 
carefully  pour  off  most  of  the  fluid. 

(3)  Add  more  water  and  mix  as  before. 

(4)  Cover  another  vessel  with  surgeon's  lint,  fastening 
same  with  cord  or  adhesive  plaster,  and  pour  the  mix- 
ture upon  the  gauze. 

In  the  detritus  left  upon  the  gauze,  search  for  gall- 
stones, parasites,  or  any  other  foreign  object.  In  place 
of  the  lint,  a  fine  sieve  may  be  used  with  which  to  strain 
the  mixture.  Gall-stones  vary  in  size  from  a  grain  of 
sand  to  an  olive  and  larger,  and  are  usually  of  a  brown- 
ish-green color.  They  may  crumple  to  the  touch,  or 
be  quite  hard.  Often  they  show  the  typical  smooth 
facets  on  one  or  more  sides.  The  appearance  of  para- 
sites and  the  kinds  usually  encountered,  are  described 
in  the  chapter  devoted  to  parasites. 

For  microscopical  examination  the  feces  should  be 
passed  into  a  warmed  vessel  and  sent  to  a  laboratory 


252       INFECTIOUS  AND  PARASITIC  DISEASES. 

at  once;  or  in  case  this  is  not  feasible,  a  small  portion 
should  be  poured  into  a  wide-mouthed  bottle,  and  while 
en  route  to  the  examiner  kept  warm. 

Parasites  may  be  preserved  for  longer  periods  in 
either  weakened  alcohol  or  whisky.  Gall-stones  should 
be  placed  in  a  tightly  stoppered  bottle  to  prevent  deteri- 
oration. 


APPENDIX 


WEIGHTS  AND  MEASURES. 

1.  English. 

I  grain  (gr.) 

I  ounce  (oz.) =437-5  grains. 

I  pound  (lb.) =  i6  ounces  =  7000  grains. 

I  minim =.91146  grain. 

I  fluidram =60  minims. 

I  fluidounce =8  fluidrams, 

I  pint =20  fluidounces. 

I  gallon =8  pints. 

2.  Relations  of  English  and  Metric  Systems. 

I  grain =64.8  milligrams. 

I  ounce =  28.3  grams. 

I  pound =453.6  grams. 

I  gram =15.432  grains. 

I  kilo =2  pounds  3  ounces. 

I  minim =0.059  cubic  centimeter. 

I  fluidram =3-5  cubic  centimeters. 

I  fluidounce =28.39  cubic  centimeters 

I  pint =567.9  cubic  centimeters. 

I  cu.  cm =  16.9  minims. 

I  liter =35-2  fluidounces. 

I  inch =2.54  centimeters. 

I  foot =30.48  centimeters. 

I  yard =91.44  centimeters. 

I  centimeter =o-39  inch. 

I  meter =39-37  inches. 

253 


254 


APPENDIX. 

THERMOMETRIC 

EQUIVALENTS. 

STTIGRAI 

DE        Fahrenheit 

Centigrade       F 

ahrenh 

IIO 

230 

38 

100.4 

lOO 

212 

37.5 

99.9 

95 

203 

37 

98.6 

90 

194 

36.5 

97-7 

85 

185 

36 

96.8 

80 

176 

35-5 

95-9 

75 

167 

35 

95 

70 

158 

34 

93-2 

65 

149 

33 

91.4 

60 

140 

32 

89.6 

55 

131 

31 

87.8 

50 

122 

30 

86 

45 

113 

25 

77 

44 

III. 2 

20 

68 

43 

109.4 

IS 

59 

42 

107.6 

10 

50 

41 

105.8 

+  5 

41 

40.5 

104.9 

0 

32 

40 

104.0 

-  5 

23 

39-5 

103. 1 

—  10 

14 

39 

102.2 

~i5 

+  5 

38.5 

101.3 

—  20 

-   4 

Formulae  for  converting  degrees  of  Fahrenheit  into  Centigrade 
and  vice  versa. 

F.  =  Fahrenheit;     C.  =  Centigrade;     D.=degrees. 
Fahrenheit  into  Centigrade 

(F.-32°)X|=C. 
Example:  140°  F.=r  140-32 X|=6o°  C. 
Centigrade  into  Fahrenheit 

(C.X|)+32=F. 
Example:  io°  C.=ioX|+32=5o°  F. 


INDEX 


Abscess,  amoebic,  107,  112;  for- 
mation of,  106,  107;  from  bot- 
fly, 142;  from  flea,  144 

Actinomycosis,  epitome  of,  184 

Adolescence,  typhoid  fever  and 
tuberculosis  in,  97 

Age,  influence  on  disease,  94-98 

Agglutination,  27;  agglutinins  in, 
27 

Ague,  198,  199 

Albumin,  tests  for,  in  urine,  246 

Amoebic  dysentery,  112 

Antibodies,  25,  99 

Antiseptics,  definition  of,  57 ; 
sugar  and  salt,  58 

Antitoxin,  25,  30 

Anthrax,  epitome,  185 

Armed  tape- worm,  137 

Arsenical  poisoning,  4 

Ascaris  lumbricoides,  124 

Asiatic  cholera,  temperature  in, 

19 
Asiatic  lung  fluke,  130 

Bacilli,  44 

Bacilluria,  160 

Bacteria,  38;  aerobic  and  anaero- 
bic, 56;  agents  harmful  to,  57; 
air,  49;  arts  and  industries, 
39;  in  complications,  32;  dis- 
tribution, 45-50;  in  dust,  47, 


48 ;  effect  on,  drying,  light, 
ozone,  heat,  etc.,  60-63;  ^^^^s 
from  body,  152;  expectoration 
and  nasal  secretions,  155;  fac- 
tors necessary  for  growth,  53- 
57;  in  feces.  156;  forms  of,  43; 
grouping,  44;  ground,  47;  in 
inflammations,  105;  multipli- 
cation, 42;  pathogenic  and 
non-pathogenic,  41;  shape,  43; 
size,  42;  skin,  exit  from,  161; 
specific  and  non-specific,  51; 
spores,  52;  suppurations,  exit 
in,  164;  thermal  death-point, 
217;  in  urine,  160;  virulent 
and  non- virulent,  41;  vomit, 
156;  in  water,  48 

Bacteriaemias,  20 

Bactericidal,  27 

Bacteriolysins,  27 

Balsam  Peru,  specific  in  itch,  148 

Bed-b^gs,  144 

Bichloride  of  mercury,  221 

Bilharziosis,  132 

Black  death  (see  bubonic  plague) 

Bladder- worms,  135 

Blood,  examination  of,  236;  for 
malaria,  238;  for  typhoid  fever, 
236;  exit  for  infectious  agents, 
162 

Boas,  test-breakfast,  235 


255 


256 


INDEX. 


Bot-flies,  142,  143 
Break-bone  fever  (see  dengue) 
Bubonic    plague,   epitome,    186, 

187 

Carbolic  acid,  disinfectant,  222 
Cestodes,  133 
Chemotaxis,  103 
Chicken-pox,  epitome,  188 
Childhood,  diseases  of,  96 
Cholera,  epitome,  189 
Climate,  a  predisposing  cause,  81 
Coccidium  hominis,  11 1 
Cold-storage,  danger  of,  179 
Combined  infections,  22 
Communicable,  37 
Complications,  32 
Compsomyia  macellaria,  143 
Congenital  infections,  182 
Contagious,  36 
"  Core,"  of  abscess,  107 
Cover-glass  preparations,  240 
Craw-craw,  filaria  in,  120 
Creeping  eruption,  173 
Crisis,  18 

Cryptogenic  infections,  183 
Cysticerci,  135;  cysticercus  cellu- 
losa,  139 

Defensive  mechanism,  dual  ac- 
tion of,  100 
Dengue,  epitome,  190 
Deodorant,  definition,  57 
Dermatobia   cyaniventris,     143 ; 

noxialis,  142 
Dibothriocephalus  latus,  137 
Diphtheria   cultures,  230 ;    epit- 
ome, 190,  191 
Disease,  agents  of,  3;  infections. 


68;  evolution  of,  34;  predis- 
posing causes,  74;  defensive 
mechanism  in,  2 

Disinfection  and  disinfectants, 
214;  definition,  57;  bichloride 
of  mercury,  221;  chlorinated 
lime,  224;  carbolic  acid,  222; 
formalin,  222;  heat,  216,  217; 
lime,  224;  solutol,  solveol, 
lysol,  223;  tricresol,  223 

Distomiasis,  132 

Dipylidium  caninum,  138 

Divers'  paralysis,  4 

Dum-Dum  fever,  113 

Dwarf  tape-worm,  138 

Dysentery,  amoebic,  192;  bacill- 
ary,  192 

Echinococcus  disease,  140 
Egyptian  haematuria,  132;  oph- 
thalmia, II 
Elephantiasis,  filaria  in,  119 
Epidemic  cerebro-spinal  menin- 
gitis, epitome,  188 
Erysipelas,  epitome,  193 
Evolution,  in  disease,  34 
Ewald  and  Boas,  test-breakfast, 

235 

Fasciciola  hepatica,  132 

Feces,  exit  for  bacteria  and  para- 
sites, 159;  examination  of,  249; 
gall-stones  in,  251 

Filaria  Loa,  120;  method  of  ex- 
traction, 121 

Filaria  sanguinis  hominis,  118 

Flat-worms,  129 

Flea  (pulex  irritans),  144;  sand- 
flea    (sarcopsylla   penetrans). 


INDEX. 


257 


144;  host  of  dog  tape- worm, 

138 
Flukes,  129 
Food,  danger  of  infection  from, 

175  . 
Formalin,  222 

Gall-stones,  in  stools,  251 

Genito-urinary  tract,  infections 
of,  181 

Germicide,  see  disinfectant 

Glanders,  epitome,  194 

Gonorrhoea,  epitome,  195;  infec- 
tions in  infants,  95,  96 

Guinea- worm,  116;  Soudanese 
method  of  extraction,  118 

Haematochyluria,  due  to  filaria, 

120 
Haematuria,  243 
Haemoglobinuria,  243 
Harvest-mite    (Leptus     autum- 

nalis,  149 
Health,  definition  of,  i 
Hip-joint  disease,  97 
Hook-worm,  126 
Host,  flea,  of  dog  tape- worm,  138 
Human  fertilizer,  danger  of,  176 
Hydrophobia,  epitome,  196 
Hymenolepsis  Nana,  138 

Infancy,  diseases  of,  95 
Immunity,  opsonin  in,  28 
Infectious  agents,  action,  7;  def- 
inition, 6,  7;  specific  and  non- 
specific, 9 
Infection  and  infectious  disease, 
12;  combined,  22;  contracted 
through  air  or  food,  175;  con- 
17 


veyance  by  insects,  72;  crisis 
in,  18;  family  in,  79;  general, 
19;  heredity  in,  76;  inocula- 
bility,  167;  latent  period,  14; 
lysis,  18;  mixed,  71;  number 
of  bacteria  in,  68;  portal  of 
entry  in,  69;  relation  of  body 
to,  73;  race,  76;  secondary, 
23;  self -limiting  nature  of,  24; 
specific  and  non-specific,  10; 
symbiosis  in,  71;  toxins  in,  14; 
terminal,  34;  virulence  of  bac- 
teria in,  70 

Inflanmiation,  definition,  99, 100; 
cardinal  symptoms,  10 1 

Influenza,  epitome,  197 

Insontium,  181 

Itch-mite,  148 

Intermittent  fever,  see  malaria 

Insecticides,  definition,  59 

Insects,  parasitic  of  skin,  173; 
role  in  disease,  86-90 

Ixodiasis  (tick-fever),  150 

Jews,  immunity  of,  77 
Jigger-flea,  144 

La  Grippe,  see  influenza 

Latent  period,  14 

Leprosy,  epitome,  197 

Leucocytes,  102 

Leucocytosis,  104 

Lice,    head,     146;    pubic,    147; 

clothes,  147 
Light,  effect  on  bacteria,  56 
Lime,  milk  of,  224;  chlorinated, 

224 
Liver,  influence  of  tropics  on,  84 
Liver  fluke,  Chinese,  131 


258 


INDEX. 


Liver-rot,  cause  of,  132 
Lock-jaw  (see  tetanus) 
Lues  (see  syphilis) 
Lysis,  18 

Madura  foot,  epitome,  198 

Malarial  fever,  epitome,  198, 199; 
Plasmodium  of,  11 3-1 15;  ter- 
tian and  quartan,  115 

Measles,  epitome,  119;  in  Faroe 
and  Fiji  Islands,  78 

Measles,  German  (see  rubella). 

Measles,  due  to  embryo  tape- 
worms, 139 

Membranous  croup  (see  diph- 
theria) 

Metabolism,  35 

Metastasis,  in  infections,  ^^ 

Metchnikoff,  theory  of  phagocy- 
tosis, 28,  103 

Micrococci,  44 

Milk,  danger  of,  178 

Mosquitoes,  in  filariasis,  120; 
malaria,  73,  116;  yellow  fever, 
72 

Mumps,  epitome,  200 

Mountain-climber's  disease,  3 

Mouth,  portal  of  entry,  174 

Myiasis,  141 

Napoleon,  sufferer  from  itch,  148 
Necrobiosis,  106 

Occupation,  predisposing  to  in- 
fections, 92-94;  mortaHty  table, 
92 
Old  age,  pneumonia  in,  97 
Ophthalmia     neonatorum     (see 
gonorrhoea) 


Opisthorchis  sinensis,  131 

Opsonin,  27 

Organism,  6 

Osier,    prophylaxis    in    typhoid 

fever,  211 
Oxygen,  relation  of,  to  bacteria, 

,    55    . 

Oxyuris  vermicularis,  125 

Painters'  colic,  4 

Parasite,  definition,  8;  kinds,  109; 
cycle  of  development,  no 

Parasites,  exits  from  body,  152; 
expectoration,  156;  skin,  162, 
173;  suppurations,  165;  feces, 
159;  urine,  161;  vomit,  156 

Parasitic  flies,  141 

Parasitic  haemoptysis,  130 

Paragonimus  Westermanii,  130 

Phagocytosis,  104;  opsonin  in,  28 

Pin  worm,  125 

Pneumonia,  epitome,  200;  as  sec- 
ondary infection,  23 

Pott's  disease,  97 

Predisposition,   74;   age,  94;  in- 

,'   fluence  of  region,  climate,  81; 

^individual,  80;  inherited  and 
acquired,  80;  family,  79;  phys- 

.^Jical  conditions  of  country,  85; 

.  .occupation,  92 

Proglottides,  of  tape- worm,  134 

Protozoa,  6,  in 

Ptomain  poisoning,  4 

Pus,  107 

Pyaemia,  21 

Pyogenic  bacteria,  107;  in  infec- 
tions of  childhood,  97 

Quick  consumption,  21 


INDEX. 


259 


Relapsing  fever,  epitome,  201 
Riegel,  test-dinner,  235 
Round- worm,  124 
Rubella,  epitome,  202 

Saprophytes,  40 

Sarcophaga  Carnaria,  143 

Scarlet  fever,  epitome,  202;  ten- 
acity of  virus,  155 

Schistosomum  haematobium,  132 

Screw  worm,  143 

Season,  influence  on  predisposi- 
tion, 90 

Secondary  infections,  23 

Septicaemia,  20 

Skin,  exit  for  bacteria,  161;  portal 
of  entry,  173 

Sleeping  sickness,  113 

Snail,  host  of  Bilharzia  haema- 
tobium, 133 

Small-pox,  epitome,  203,  204 

Spirilla,  44 

Spores,  52;  disinfection  of,  218 

Sputum,'examinationof,  226-229; 
exit  for  bacteria  and  parasites, 
156;  collection  of,  229;  mum- 
mular,  228 

Staphylococci,  45 

Stegomyia  fasciata,  in  yellow 
fever,  89 

Stomatitis   (epidemic),   epitome, 

205      . 
Sterilization,  definition,  57 
Streptococci,  45 
Strongyloides  intestinalis,  122 
Sugar,  test  for,  in  urine,  247 
Suppuration,  106;  exit  for  infec- 
tious and  parasitic  agents,  164 
Syphilis,  epitome  of,  206 


Taenia  saginata,  136;  taenia  sol- 
ium, 136 

Tape-worms,  133;  beef,  136; 
dwarf,  138;  dog,  138;  fish, 
137;  pork,  136;  segments  in 
vomit,  156 

Temperature,  effect  on  bacteria, 

55 

Terminal  infections,  34 

Test-meals,  234 

Tetanus,  epitome,  207 

Thread- worm,  125 

Tick-fever,  150 

Toxaemias,  20 

Toxins,  14,  20 

Trematodes,  129 

Treponema  (spirochaeta)  palli- 
dum, II 

Trichinella  spiralis,  122 

Trichiniasis,  122 

Tricresol,  223 

Tropics,  predisposing  influence, 
81-86 

Trypanosomiasis,  113 

Tuberculosis,  epitome,  208;  in 
children,  80;  among  Jews,  78; 
negro,  78;  North  American 
Indian,  78;  as  secondary  in- 
fection, 23 

Typhoid  fever,  epitome,  209- 
212;  without  intestinal  lesions, 
170 

Ultra-microscopic,  11 

Uncinaria  duodenalis,  126;  Amer- 
icana, 127 

Urine,  albumen,  tests  for,  246; 
bile.  Smith's  test,  243;  collec- 
tion, 248;   examination,  241; 


26o 


INDEX. 


specific    gravity,    245 ;    sugar 
test,  247;  typhoid  bacilli  in,  160 

Variola  (see  small-pox) 
Vomit,  occurrence,  232;  exami- 
nation, 233-235 

Water-borne  diseases,  49 
Whip- worm,  121 


Whooping-cough,  epitome,  212 
Widal  reaction,  236 
Wood-tick,  149 

Wool-sorter's  disease  (see  an- 
thrax) 

Yellow  fever,  early  methods  of 
disinfection,  168;  epitome,  212; 
U.  S.  Army  conmiission,  163 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 

Los  Angeles 
This  boo^^UE^j^  la.,  date  s,amped  below. 

^  MAY  0711 

MAY  4 


la 


3    ■filL. 

^   i'o8  00155  2917 


^ 


SOUTHERN  BRANCn, 

yNIVERSITY  OF  CALIFMNIA, 

LIBRARY, 

iLOS  ANGELESp  SALIR 


